AAPT2: Separate out the various steps

An early refactor. Some ideas became clearer as
development continued. Now the various phases are much
clearer and more easily reusable.

Also added a ton of tests!

Change-Id: Ic8f0a70c8222370352e63533b329c40457c0903e
diff --git a/tools/aapt2/ConfigDescription.cpp b/tools/aapt2/ConfigDescription.cpp
index 6ddf94a..8120fa7 100644
--- a/tools/aapt2/ConfigDescription.cpp
+++ b/tools/aapt2/ConfigDescription.cpp
@@ -17,8 +17,8 @@
 #include "ConfigDescription.h"
 #include "Locale.h"
 #include "SdkConstants.h"
-#include "StringPiece.h"
-#include "Util.h"
+#include "util/StringPiece.h"
+#include "util/Util.h"
 
 #include <androidfw/ResourceTypes.h>
 #include <string>