Allow User select Tablet Mode

Device overlay variables for tablet mode on Grouper
Needs other Tablet UI commits.

Change-Id: I466ffa9dac9e5e553d37855f8e8d153fc583e5a0
Signed-off-by: Zaphod <mwilson@acesappraisal.com>
Signed-off-by: DHO <DHO@dho.im>
Merge "Allow User select Tablet Mode" into jb42