Python thin: python directory should be included in binary release

Currently, python directory is not generated by the maven install command. Need to add appropriate copy steps to assembly/release-fabric-base.xml file.

The following components should be copied:

ignite/modules/platforms/python/pyignite/**
ignite/modules/platforms/python/requirements/**
ignite/modules/platforms/python/LICENSE
ignite/modules/platforms/python/README.md
ignite/modules/platforms/python/setup.py

(** stands for "all the files and sub-folders recursively, starting from
this folder".)