[Android] Generate resource maps for internal packages

The resource maps are removed from upstream commit 866abeb.
Crosswalk need these resources entries to resolve the
conflict of how Resource Ids generated between gyp build
system and ant build system.
Generate resource maps from generated R.javas by crosswalk
self now.

BUG=https://crosswalk-project.org/jira/browse/XWALK-2746
naming rule of PEP-8, `res_java` and `res_map`?