add video-muted-sound and video-unmuted-sound to conference profile params

[thehunmonkgroup]

Ported from Jira: https://freeswitch.org/jira/browse/FS-7868

I find it confusing that the same file plays for both audio and video muting/unmuting, and would also like the option keep the audio mute prompts and ditch the video mute ones.

Original comment from Brian: "We need to order sound files for these too."

[mjerris]

happy to look at a pr for this. we need to think of how this will change default behavior