Fix issue #1673793: Theme styles don't apply.

It turns out this was not a problem in the resource code at all.  Rather,
the system process has a cache of pre-loaded attributes it uses to avoid
continually reloading things as it needs them.  Well it turns out this
cache wasn't flushed after a package was uninstalled or a configuration
changed, so you could re-install an app where you change its style resources
so its theme now points to one that is inconsistent in the cache.

This is mostly a problem for developers, where they continually install
new versions of an app where resources have changed.  This could possibly
show up when updating an app on a normal phone, although the problem would
eventually correct itself since this cache uses weak references.

Anyway, the cache is now reworked to be flushed appropriately.

This change also includes an update to aapt to be able to dump the
contents of bags in resources.