Themes: Support launcher based icon packs [1/2]

Before this patch, icon packs written for Trebuchet/Nova/Apex could not be used
with the new theme engine as the formats were different. Particularly the icon package IDs are 7F,
the same ID as as regular apps. Furthermore the location of resources in these icon packs was different
from what the theme engine expects. This patch adds support for these icon packs by overriding
the pkg id.

AssetManager now can override package ids without requiring aapt to recompile the APK.
Note: XML references will still use the original id compiled with AAPT, so it is only useful for resources
which do not use xml drawables (such as icon packs).

PackageInfo now has a new member identify "legacy" (3rd party icon packs) written
for launcher's like Trebuchet, Nova, and Apex.

Change-Id: Icd12c097e156c9626df0772abeb50e00f7b61f64

Conflicts:
	libs/androidfw/AssetManager.cpp
CM11 Themes: Allow defining a custom default theme [1/3]

Change-Id: I6b794d6c9c27b2d6436bdf4fec51c84a7859c134

Conflicts:
	core/java/android/content/pm/ThemeUtils.java
	core/java/android/provider/Settings.java
	packages/SettingsProvider/res/values/defaults.xml
	packages/SettingsProvider/src/com/android/providers/settings/DatabaseHelper.java
	services/java/com/android/server/ThemeService.java