delete() calls to a report file will move it into sdcard storage

This is a patch to get #1255 in so that delete() calls to a report file will actually move it into sdcard storage.

Most of the code here is actually robolectric related test code.  Important bits to note are:

* There is a test that exercises the checkbox in the DeveloperActivityFragment and setting the pref
* There is a test that makes sure that the SDCARD is mounted
  * the sdcard may be in an unmounted state, but robolectric will let you write to it anyway.  There doesn't seem to be a good way to test or mock this out.
* There is a test to verify the toast string
* There is a test to make sure files are moved from the report directory to the sdcard archive path.
Can we pull out this new logic to a client-side subclass?