Bug 858416 - Test gaia app for exercising device storage.

Also adjusts the settings app to use storageName instead of volumeName
since bug 858416 renamed this field.
Merge pull request #9696 from dhylands/dhylands-838038-ds-test-app-master

Bug 858416 - Test gaia app for exercising device storage. r=dougt

There may be some brokeness in the Media Storage area of the settings app until the patch from birch shows up.