CRS transformations

[andrea-bistacchi]

With 502c560 I added 2D CRS transformations with PROJ wrapped as pyproj - the worldwide standard in geographic/geodetic projections and transformations.

Only the transformation of entities exposing the .points property is accurate, i.e. performed on each point X, Y coordinates. Objects with a regular grid, such as images, are transformed with a simple 2D roto-translation obtained as the best-fit transformation of the bounding box.

[andrea-bistacchi]

To be done for XSections:

• calculate a roto-translation to be applied to all entities
• write a new method in the x-sections collection to set all metadata and the plane from the frame (*)
• write a loop to transform all entities belonging to the cross section with the roto-translation

To be done for regular grids (Voxet, XsVoxet, MapImage, XsImage, Image3D):

• calculate a roto-translation to be applied to the grid