Correct some lint warnings

Correcting lint issues such as:
 - if -> switch
 - unnecessary (un)boxing
 - for / while -> foreach where appropriate
 - remove unused imports
 - remove obsolete SDK_INT checks

Change-Id: Icb7170b0564b9c1cf191a0a102d1babab61e2ec2
Signed-off-by: Alexander Martinz <amartinz@shiftphones.com>