ARI: Add support for suppressing media streams.

Also convert res_mutestream to use the core feature behind this.

(closes issue ASTERISK-21618)

Review: https://reviewboard.asterisk.org/r/2652/


git-svn-id: http://svn.asterisk.org/svn/asterisk/trunk@394715 f38db490-d61c-443f-a65b-d21fe96a405b