Some more code cleanup and re-work in the development trunk.

• cleanup initialisation of OSD position and int array config items.
• move functions related to 'user' menu to 'gui_user_menu.c' and gui_user_menu.h' files.
• move code for OSD layout editor to 'gui_osd_edit.c', converted to a module so only loaded when actually changing the OSD layout.
• cleanup of OSD display functions in gui_osd.c.