Laserchicken

Fixed
- select_polygon now works with shapely 2.0

Changed:
- continuous integration moved from travis to GH actions
- naming of band ratio's modified (symbol "<" dropped from label)

Added
- releases published on PyPI using GH actions
- checklists included

Fixed
- Fixed import of deprecated `scipy.stats.stats`

Changed:
- update documentation with table of features
- drop python 3.5 due to problematic lazperf dependency, includes CI on python 3.7 and 3.8
- drop usage of pylas (deprecated) in favour of laspy, with lazrs backend for LAZ compression

Fixed
- minor fixes following updates in dateutils/click

Added:
- faster implementation of spatial selection

Changed:
- all elements in WKT and shapefiles containing multiple polygons are considered (not only the first element)
- the validity conditions for multipolygons have been relaxed: valid adjacent polygons are now accepted

Fixed:
- bug in copy_point_cloud with masks and zero-filled feature-arrays

Added:
- select_equal filter accepts list of values to compare to the points' attributes
- also the attribute-based filter functions optionally return a mask to allow filter combinations

Fixed:
- bug in writing/reading 'None' as parameter in the PLY comments

Added:
- build_volume module
- the most relevant functions can be now imported directly from laserchicken
- reading/writing of binary PLY and LAZ files, with optional writing of selected attributes
- utility function to merge point-cloud data
- extra log tasks implemented: point-cloud log entries are introduced upon point-cloud loading, filtering, normalizing, merging and assigning to targets.
- select_polygon now supports multi-polygons and optionally return a mask for the selected points

Changed:
- compute neighborhoods returns generator with neighborhoods instead of nested neighborhoods like it did before (breaking change!)
- Some of the existing modules have been renamed/restructured (breaking changes!):
- `normalization` --> `normalize`
- `feature_extraction` created (functions moved from `feature_extractor/__init__.py`)
- `select` and `spatial_selection` merged into `filter`, with the function `select_polygon` allowing to deal with all the spatial selection functionalities
- format-specific `read_*` and `write_*` modules replaced by `load` and `export`
- Dependency on `laspy` replaced by `pylas` + `lazperf` (easier reading/writing of LAS/LAZ files)