Add a new plugin that uses apktool instead of aapt to rebuild apps.

[Lanchon]

This plugin would be simpler to use and produce a more faithful app to the original than the current 'patched-application' plugin, but would not support android's build system and in particular its resource processing. All resource edits would need to be done in apktool's output, and adding android libraries, etc would not be possible. This plugin would be especially useful for cases in which you just want to edit code.