Pyinterpolate

* neighbors selection (lags counting) has been changed,
* `TheoreticalSemivariogram` searches for optimal sill in a grid search algorithm,
* corrected error in `Krige` class; now calculation of error variance is correct.

2021-12-11
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* `self.points_values` chenged to `self.points_array` in `TheoreticalSemivariogram` class,
* `NaN` values are tested and checked in `calc_semivariance_from_pt_cloud()` function,
* new semivariogram models included in the package: **cubic**, **circular**, **power**,
* corrected calculation of the closest neighbors for kriging interpolation,
* changed `prepare_kriging_data()` function,
* the new optional parameter `check_coordinates` (**bool**) of `calc_point_to_point_distance()` function to control the coordinates uniqueness tests. This test is very resource-consuming and should be avoided in a normal work and it should be performed before data injection into the modeling pipeline.
* the new `dev/profiling/` directory to test and profile parts of a code.

2021-08-23
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* the outliers removal function: you can choose side for outlier detection and remove. Default is top, available are: both, top, down,
* the outliers removal function: changed algorithm,
* new tutorial about outliers and their influence on the final model.

2021-05-13
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* more parameters to store (and access) in TheoreticalSemivariogram class,
* error weighting against the linear regression model (ax + b),
* global mean for Simple Kriging as a required parameter,
* tqdm progress bar to `RegularizedSemivariogram.transform()` and `interpolate_raster()` functions,
* refactored Semivariogram Regularization: ranges are controlled by algorithm, not an user,
* added pull request template,
* added issues templates,
* bug in spherical semivariogram model,
* experimental variogram as points (not a solid line),
* inverse distance weighting function: algorithm, tests, documentation and new tutorial,
* changed output names of regularized data (`ArealKriging.regularize_data`) from **estimated value** to **reg.est** and from **estimated prediction error** to **reg.err**,
* error related to the id column as a string removed,
* TheoreticalSemivariogram `params` attribute changed to `nugget`, `sill` and `range` attributes.

2021-03-10
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* directional semivariograms methods, docs and tests added,
* check if points are within elliptical area around point of interest method, docs and tests added,
* broken dependency in `README.md` corrected.

2021-03-02
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* variogram point cloud methods, tutorials, docs and tests added,
* updated tutorials and baseline datasets to show examples with spatial correlation,
* updated `README.md`: contribution, example, sample image,
* data is tested against duplicates (points with the same coordinates),
* removed bug in `interpolate_raster()` method.