Add setting to mute/unmute the Mycroft-core endpoint that the Android app talks to.

[seymour-bootay]

adding a setting to mute/un-mute the mycroft-core endpoint (raspberry pi for most).

[seymour-bootay]

the complication with having the switch in the phone is that it will need to query mycroft-core to determine if it currently muted or not. This will require a change to the volume skill in core.

If you want just the phone to answer mute the mycroft-core endpoint by saying "mute volume" either in range of the mic or through the android app.

to unmute the mycroft-core endpoint say "set volume default"