Kazuto's patches for the groovy app manager.

These are from kazuto's large pull request: 

https://github.com/rosjava/android_core/pull/154/files

but without the app manager parts (better not in core since it will update and change frequently) and I changed the bar scanner intent result to handle either text type or qr codes.

@KazutoMurase can you give some detail?

* Should RosActivity's `NodeMainExecutorService` and `startMasterChooser` be protected/public? Is that necessary for the app manager?
* Exactly what problem were the clearHandle's solving?