Add option to developer options to enable FPS counter

Signed-off-by: Simon Busch <morphis@gravedo.de>
Rename Developer Mode page to Developer Options

Signed-off-by: Simon Busch <morphis@gravedo.de>
Remove developer mode from devmode page

A developer mode isn't yet implemented within the whole system and will not be for beta so
we drop the option for until we have something.

Signed-off-by: Simon Busch <morphis@gravedo.de>