Remove media between tests, and push resources to storage for tests that require them

This means a few things:
* SD Card will not fill up with photos, videos, etc
* No need to push files to the device for tests
* We can write tests for gallery, video player, music player, etc when no content is present
* All test runs use the same files, so results should be more consistent

This also should work on Panda using SUT agent, but I have not tested this.