CM11 Themes: Common overlay for sharing resources. [1/2]

This patch will allow themes to contain common resources
which can be shared by all overlays.

Common resources will reside in assets/overlays/common and
can be referenced by other overlays.

Common resources will be referenced using the common package
name, i.e. To reference the common drawable some_drawable for
com.example.theme the theme designer would use
"@*common:drawable/some_drawable"

Change-Id: I395b6bd5eae91b00265a8e9221856ef7bf5d115a
CM11 Themes: Include alarms in mixnmatch.

Change-Id: I004f6b0149d71c8ed1a3952704f5a3521eca5add
CM11 Themes: Properly handle SystemUI theme package name.

Change-Id: Ia8915684e1620184dcc513c2c5039ea20aabbd04
Merge "CM11 Themes: Include alarms in mixnmatch." into cm-11.0
Merge "CM11 Themes: Common overlay for sharing resources. [1/2]" into cm-11.0
Merge remote-tracking branch 'upstream/cm-11.0' into cm-11.0