Asset redirections are now managed by a system service.

Adjusted the asset redirection design to use a common system service
(AssetRedirectionManagerService) for synchronization and cache
management.  This replaces the old /data/res-cache design completely
(nothing is written to disk now).

This change also moves a large amount of code from the C++ layer to Java
for parsing the theme meta data and redirection XML files, though the
actual redirection still occurs at the native layer.

Change-Id: I8820e39425135269f5e723534c4b9c8dc6841779