Merge pull request #656 from Markismus/master

Persistent defaults.lua option added.
Merge pull request #661 from Markismus/master

Offset and resize Kobo Aura screen because of obscuration by black bezel
Delete KoboAuraTapHomeIcon.bin

Pazos' change of koreader_kobo.sh makes these binary files obsolete.
Delete KoboMiniTapHomeIcon.bin
Merge pull request #662 from Markismus/master

Now button events are passed to koreader and it exits cleanly to Nickel