fb: TRDS some tweaks and fixes (1/2)

some smaller issues fixed and optimizations:

- fix twilightmode was wrong assigned to wrong value
- ligtsensor mode after first immediattely switch it does
  not allow for 5sec to switch again....after the 5sec it switches
  to current state if the sensor changed its state in this time.
  This prevends on the one hand on bad light conditions a permanent
  switch between dark/light as well it does not bring the system into
  troubles due of to much configuration changes at the same time
- get rid completly of the observe for the UI_THEME_MODE value and
  handle all over the UIModeManager
- some cleanup and minor fixes

Change-Id: I4b2401bf7bef992ad3112ae5ccc852cd29b46bd0