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
Send broadcast when package is 'about' to be removed

If a theme package is removed and it is the currently applied
theme, some apps will crash because the theme resources are
no longer available, since they were cleaned up by the package
manager.  The themes provider will receive this broadcast and
take care of switching back to the default theme for components
that are using the package about to be removed.

Change-Id: I968c25e19eb17ec87e7ddcba5ac0fd81745cef20
Merge branch 'kitkat' of https://github.com/task650/frameworks_base into kitkat