Add keyboard shortcuts for all UI actions

[hosy]

Expected behaviour

Users should have the possibility to control the app completely with keyboard shortcuts. This is a feature for power users and will give our app a final touch.

e.g.
File list view:
CMD + N can show the "Upload file" menu

Actual behaviour

Keyboard shortcuts are implemented only in the passcode view.

Client

ownCloud app version:
1.0.0

Device model:
iPad

[jesmrec]

Already done