Implemented power button based shutdown and tidyup via dbus

[twobob]

Could be tidier, but it works.

[PaulFreund]

Hey twobob, thanks for helping me with this, but I don't fully understand why we need this, is it because the paperwhite does not have a button? If so, how can one escape then ( with the help of this fix )

I restore the status bar when I exit the application already, could it be possible to do this with the (I think this is the desired behaviour )toggle power button too ( I think it could be possible, but I would need an exact description what it does )?

Anyway, I'll merge this and do the other improvements, well get back on that later

[twobob]

Um... the PW has a power button on the bottom.

I could not find a way to "close down the app" other than this.

My devices PREVENT going to screensaver "by default" at boot time. As do the devices of others.

If I missed something let me know but being able to "Tap Out" via the power button is pretty standard now on PW apps (given the no HOME button scenario and it being the only "button")