(1/2) Add status bar battery icon configuration.

Many people resort to editing the compiled frameworks to remove the
battery icon on the status bar. This patch set adds an new option in
CMParts to select between the stock icon, the CyanogenMod percentage
meter, or no battery status at all.

By default the stock battery icon is shown.

Part 2/2: I2cb73df37a4857288dae6ffabb8652c37d76a8ca

Change-Id: Ie73690cfa465f0299f8904cb4f3690898614eb71