RcModel: refactor to allow support of all receivers

RcModel: refactor to allow support of all receivers

Remove subdir level per rc model.
Each Rc has now a xml and png file name after the Rc model.
A separate config file (rc_models.cfg) maps different Rc options
for a box to the specific rc mode.
This simplifies the code and allows for adding new boxes and
Rc models in a simple way (just add a png and a possitions xml
file, and add mappings to the config file)

This new code will dynamically follow the setup menu for changing
Rc type/model!