Centerline-width

Update to Back End for plotCenterlineWidth()

Update accounts for the curvature of the Earth when calculating the slope for width with `plotCenterlineWidth()`

Previously, slopes were calculated based on `transect_span_distance` without accounting for the curvature of the planet. Updated functionality now accounts for the curvature of the planet (defined by `ellipsoid`, defaults to `WGS84`). Adjusts positions where width lines intersect banks.

Previous (left) and updated (right) places where width lines intersect bank


Area of River
Return the area contained within the polygon generated the left and right bank latitude/longitudes

river_object.riverArea

Area returned in kilometers^2
python
import centerline_width
river_object = centerline_width.riverCenterline(csv_data="data/river_coords.csv")
river_area = river_object.riverArea


Code Coverage
New code coverage and testing to track back end of repo

Expanding pytests to coverage existing functionality for centerline and widths (~93%) error handling and expected outputs

Backwards Compatibility Conflicts

`convertColumnsToCSV()` argument `flipBankDirection` changed to `flip_direction` to be consistent with snake-case variable naming conventions among other functions

Drops active support for Python 3.9 in support of [NEP 29](https://numpy.org/neps/nep-0029-deprecation_policy.html)

_Bug fixes and README.md edits_

_Pytests: Tests for Python 3.10, 3.11, 3.12 against Ubuntu, macOS, Windows_

New options: show_plot

New option `show_plot` and the option to use relative paths. New options are optional and backwards compatible, so there should be no impact on existing scripts.

**show_plot**

New option in `plotCenterline()` and `plotCenterlineWidth()`

New option to not show a newly generated plot. The plot will still save if `save_plot` is still in use. Useful when running `centerline-width` as part of a loop to save multiple plots without having to close each plot after it is generated. `show_plot=False` is the same as not using plt.show() in Matplotlib.

**Relative Paths**

New back-end option to use a relative instead of absolute path when `convertColumnsToCSV()`


relative path: file_path = "../../B/aaa.txt"
absolute path: file_path = "test/testing/B/aaa.txt"


**Python 3.12 Support**

Expanded testing suite and verify support with Python 3.12. Currently supporting Python 3.9, 3.10, 3.11, 3.12

**Developer Environment**

New conda environment file `environment.yml` for working with or testing against the `centerline-width`

_Bug fixes and README.md edits_

_Pytests: 233 tests for Python 3.9, 3.10, 3.11, 3.12 against Ubuntu, macOS, Windows_

New Options: `equal_axis`, `transect_slope`, `dark_mode`
All new options are optional and backwards compatible so there should be no impact to existing scripts

equal_axis

Closes: 4 where perpendicular width lines do not appear perpendicular

equal_axis will set the x and y axis of the plot to be equal. Useful to show the perpendicular width lines as perpendicular since it can appear distorted by default in Matplotlib

| equal_axis=False | equal_axis=True |
| ------------- | ------------- |
|  | |

transect_slope
The width lines are generated as perpendicular to the slopes of the points across `transect_span_distance`

By default, `transect_slope="Average"` where the width lines are perpendicular to the average slopes of the across span distance. For example: `[A, B, C, D] = avg( slope([A, B]) + slope([B, C]) + slope([C+D]) )`

Optionally, if `transect_slope="Direct"` then the width lines will be perpendicular to slope of the first and last point. For example: `[A, B, C, D] = slope([A, D])` to avoid being susceptible to rapid small changes along the centerline

| transect_slope="Average" | transect_slope="Direct" |
| ------------- | ------------- |
|  |  |

dark_mode

New smart dark mode option when generating Matplotlib (for long suffering eyes)

| dark_mode=False | dark_mode=True |
| ------------- | ------------- |
|  | |

Additional Changes:
- `transect_span_distance` minimum has been change from 3 to 2 (to measure a single slope)

Note: Re-release of 1.4.0 with hot fix for PyPi package

__Bug fixes and README.md edits__
__Pytests: 229 tests for Python 3.9, 3.10, 3.11__

New Option for riverWidthFromCenterline: coordinate_reference
New option for `riverWidthFromCenterlinen()` to reference a width line
- Two options: `Centerline` and `Banks`
- By default, `coordinate_reference="Centerline"` where width lines are referenced in respect to the centerline coordinate that it intersects
- New option, `coordinate_reference="Banks"` where width lines are referenced in respect to the right and left banks that it intersects (resolves: 1)
- No changes to existing behavior and function is backwards compatible

More details: [riverWidthFromCenterline](https://github.com/cyschneck/centerline-width#return-width-of-river)

Bug fix: centerlineLength()
Length was being calculated incorrectly as the pairs of coordinates being calculated were not correctly updating (A->B + A->C, fix: A->B + B->C)

Thanks to mthaddon for identifying the bug and PR fix 2 🎉

_Bug fixes and README.md edits_

_Pytests: 211 tests_

Bug Fix: riverWidthFromCenterline()
Fix allows for width from centerline to be saved to a csv
- Bug introduced when `coordinate_type` renamed to `coordinate_unit`
- Backend updated: new script saveOutput.py
- saveOutput.py: saveCenterlineCSV() and saveCenterlineMAT() moved to a separate script

Inclusive of all points
`left_bank_relative_coordinates` now inclusive for all points
- Includes the first point of the left bank to be a Relative Distance of (0,0)

_Bug fixes and README.md edits_

_Pytests: 205 tests_

coordinate_type renamed to coordinate_unit: "Relative Distance" vs. "Decimal Degrees"
Original argument renamed from `coordinate_type` to `coordinate_unit`

Change can impact backward functionality in:

- plotCenterline()
- plotCenterlineWidth()
- saveCenterlineCSV()
- saveCenterlineMAT()

Fix to `riverWidthFromCenterline()`
Returns accurate coordinates and width size when using `coordinate_unit = "Relative Distance"`

_Bug fixes and README.md edits_

_Pytests: 205 tests_