fix(kobo): partially fix suspend support

Tested in Kobo Aura HD.

Suspend can still be interrrupted if user touches the screen after
slided the power button and before the suspend function is called (2s delay).

Reason for this is still unkown.
feature(device): add isKindle method
refactor(uimanager): use event_handlers to dispatch events
fix(kobo suspend): ignore user input in suspend mode
Merge pull request #669 from houqp/kobo_suspend

Kobo suspend support