Cache resource ID lookups in aapt

This speeds up certain workloads considerably, particularly
those involved in buildling apps via the SDK.  Windows-based
use should particularly benefit from the change.

Change-Id: I29f4b3a77400b201ee219729cc28a5e359c0c5e8

Conflicts:

	tools/aapt/ResourceIdCache.cpp
	tools/aapt/ResourceIdCache.h

Signed-off-by: travp624 <travp624@gmail.com>