Code factorization on EmType select and unselect fields. Added comparison capabilities to EmComponent (and childs)
Implemented __hash__ and __eq__ for EmComponent (based on class name and uid) to test equality betwenn two instance. Allows to use "instance in instance_list" syntax
Added docstrings comments to tests and fixed "false hidden failure"
Added docstrings comments to tests (for fancy output with -v ).
Fixed strange hidden failure that make tests stops on non failed tests with -f option. Those false failure seems to comes from with self.subTest blocs with functions calls that does assertion.