Pycatia

* Added new document type CatalogDocument.
* Added new document type CATMaterial.
* fixed method for AxisSystem.origin_point, AxisSystem.x_axis_direction, AxisSystem.y_axis_direction and
AxisSystem.z_axis_direction. (Mithro86)
* Added warning to example__assembly_convertor__001.py for when writing to files. (deloarts)
* fixed method for Limit.limiting_element(). (ptm-tm)

* fixed method for VisPropertySet.get_show(). (Mithro86)
* fixed method for AxisSystem.get_vectors(). (Mithro86)
* Partial fix to Selection.indicate_or_select_element_3d(). (Mithro86)
* added pathlib.Path to DrawingPictures.add().
* now tries to get the Windows absolute path from input as CATIA may not be able to otherwise find the file.
* References to python 3.6 now updated to 3.9 due to type annotation support.
* fixed method for Line.get_direction(). (Mithro86)

* fixed method for DrawingDimension.get_tolerances()
* fixed method for DrawingDimension.get_clip().
* added new method shape_factory.add_new_symmetry_2 (deloarts).
* added example
* restructured examples into categories.

* added material interfaces (deloarts). See examples.
* fixed Documents.read(). It now returns a pycatia document object
(Alexander via email).

* fixed method in pycatia/hybrid_shape_interfaces/hybrid_shape_plane_offset_pt
* fixed method in pycatia/product_structure_interfaces/assembly_convertor.print

* fixed methods in pycatia/mec_mod_interfaces/axis_system and pycatia/mec_mod_interfaces/cylindrical_face.py that
required mapping to VBA methods.