Redesign intent Mute/Unmute

[davbl]

• Cover "Hey Mycroft mute" use case, without requiring "audio", "volume" etc. (Volume.voc) in the phrase. I.e. allow both "HM mute" as well as "HM mute audio" etc.

• Remove "silence" from the mute intent and let "HM silence" and "HM silence audio" be handled by the Stop skill. Saying "silence" usually isn't intended to mute, just to stop.

• In the same way as with mute intent, allow "HM unmute" without requiring "audio" or "volume" in the phrase.

• Make "reset" from the Unmute.voc work not as unmute but to reset the audio level to default (I think it's 6), i.e. as a different intent. (Keep "restore" +Volume.voc as unmute intent.)

• Make Mycroft not reply "Audio is going to be muted", just go to muted state without saying anything and...

• Indicate the muted state visually, see picture (Mark I face):