Settings: Hover options (2/2)

add some user options to the Hover feature:
  - enable/disable
  - hide Hover button
  - force require fullscreen
  - exclude nom clearable notifications
  - exclude low priority notifications
  - exclude foreground app
  - selectable timeout delay

option menu is shown on hover toggle longpress and is launched in a floating window
fragment calls settings preference as a setting shortcut

Change-Id: Ic7c0cefd68ec11a54d0ae94485f8ca4967383122