Settings: Handle navbar heights correct on dpi changes + more (2/2)

Till now we set the height in px in the settings. Which is a problem
especially on multiDPI roms like we are when the user afterwards changes
the dpi due that it isn't calculated correct anymore on the new dpi.

This commit does
- save the dp value in provider and calculate the real px in fb
- clean up the settings stuff for it + do it a bit nicer (only settings part
  where we do not set the value for the listview)
- as well this commit disables movable navbar for tablets (we may will enable
  it in future but it needs a lot more work to have it on tablets correct working)
- add Converter class for common methods we always use....till now only px->dp
  and dp->px method
----------------------------------------------------------------------------------

PS2: Add Landscape height
PS3: Forgot this
PS4: Derp
PS5: Remove Landscape height
Change-Id: I1484f045ff80105c7bd70fe69ecd042fef42eec0
Add Landscape height for navbar [2/2]

Credits to: Nicolas Dhouailly

Change-Id: Ia6f4da6e7e0341d74c9c3b4f03f5eb106646aaa4
Signed-off-by: Lokesh Chamane <lokesh.c703@gmail.com>