Load resources from another package

While trying to build a launcher, i was looking for loading icons from other applications. I did not find a way to do this using picasso, so paf, here it is.

I have to deactivate a test, but it seems to be linked with my dev environment. No test for this improvement so far.

If you think this could be useful, do not hesitate to review and post remarks, i can work/rework on it. I'm not 100% satisfied with my current APIs, so if you have any suggestion...