[Poisson Kriging] Add directions to point selection

[SimonMolinsky]

Is your feature request related to a problem? Please describe. Using directional variograms in Poisson Kriging (like in Ordinary Kriging and Simple Kriging) would be a good idea. Now Poisson Kriging is only non-directional.

Describe the solution you'd like

• [x] Centroid-based PK - directional selection of point support and areas (will be presented in version 0.3.6),
• [x] Area to area PK - directional selection of point support and areas, (will be introduced in version 0.3.7),
• [x] Area to point PK - directional selection of point support and areas, (will be introduced in version 0.3.7).
• [x] Add warning to all directional kriging types.

Describe alternatives you've considered n/a

Additional context n/a

[SimonMolinsky]

It is still unstable part of the package, and I don't trust it at all, probably there will be some corrections in the future. There must be another issue added with a warning for those directional kriging methods...