move calls to the classes register/unregister function into register_class() / unregister_class() and add docs.
also other minor changes:
- remove face sorting keybinding, was Ctrl+Alt+F, this is quite and obscure feature and face order normally doesn't matter, so access from Face menu is enough.
- add commented out call to mesh.validate() in addon template since its useful to correct incomplete meshes during development.
- adding template of a add_object addon from Florian Meyer (testscreenings)
- this template is using the new add_utils module in bf-extensions (also from Florian)
