Refactoring widget

- Moved to com.android.email.widget
- Extracted nested classes to top-level classes
- Some small clean-ups.
- WidgetProvider and WidgetProvider$WidgetService are left in the original
  package to keep compatibility with honeycomb (3.0) release.

This CL is supposed to be pure-refactoring.  There should be no
functionality changes.

Change-Id: I37acaa24b6b488724750c0f33374b31fcc433f11
6 files changed