key presses during desklock should only be received by the lock implementation
and not by any other handler. this ensures that nothing unexpected can happen
with focus and simplifies overall key handling
after this commit, the new-but-invisible module "lokker" (or other custom loaded module) is in charge of creating all graphics for the lock screen, and it will be added to the user's config. failure to load a lockscreen module will just result in a black screen
desklock subsystem now handles all the pre/post lock stuff while the modules themselves are responsible for creating visuals and calling auth functions to determine whether to unlock the screen