Core: Cleaning usage of Android classes on core

This got in the code by my mistake on #1209
Merge pull request #1221 from DroidPlanner/coreMinorCleanUp

Core: Cleaning usage of Android classes on core
Android: Removing the unused graph widget.
Android: Removed unused class
Android: Remove unused class
Merge pull request #1222 from DroidPlanner/widgetsCleanUp

Widgets clean up
Merge branch 'master' of https://github.com/DroidPlanner/droidplanner into dp_3dr_services