Summary:
Make sure device plugins can be deeplinked as well.
(note that the duplication between `Plugin` and `DevicePlugin` is cleaned up again in D22727089, first wanted to make it work and tested, then clean)
DeepLink no longer have to be strings, per popular requests, as that makes direct linking between plugins easier (online links from the outside world have to arrive as strings)
Reviewed By: jknoxville, nikoant
Differential Revision: D22727091
fbshipit-source-id: 523c90b1e1fbf3700fdb4f62699dd57070cbc980
f8ff6dc393