Drop support for android API below 19

Starting version 2.0.0, mUzima will drop support Android versions below 19. This ticket involves creating a release branch for version 1.0.4, and refactoring master branch to reflect the support for API 19 and above, and to drop ActionBarSherlock.

Reasoning to drop Andriod versions below 19:
From current market stats, most android devices use Andriod 4.4 and above. It is costly and timely to support very small % on the devices that use below Android 4.4.