[Merge] lp:~chunsang/media-hub/wip_media-hub-interface into lp:media-hub

[Alfonso Sanchez-Beato]

@chunsang, thanks for the changes. After some testing, I have some further comments:

* In the end, the line
name: "MediaHub"
is actually needed. It works as a parameter to the mpris interface, and gets used to build the apparmor profile. Please add it back, plus a comment on why it is needed.

* Add the screen-inhibit-control to the list of plugs, this is needed so media-hub can control the screen display.

* I see a couple of warnings when creating the snap:
<<
"grade" property not specified: defaulting to "stable"
DEPRECATED: The 'snap' keyword has been replaced by 'prime'.
See http://snapcraft.io/docs/deprecation-notices/dn1 for more information.
>>
Please remove them (add grade: stable and use prime)
-- 
https://code.launchpad.net/~chunsang/media-hub/wip_media-hub-interface/+merge/319896
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