Navigation bar ring targets
Explanation of changes done to ModLockscreen:
GlowPadView related logic has been moved into a separate class for
better reusability (avoids redundancy).

TODO: make ring targets appear correctly for vertical navbar (when in landscape mode)

Cherry-picked and backported from KitKat branch

Revised by bgcngm:
- Take into account specific MTK GlowPadView for keyguard