Microphone volume adjustment

[commsys]

It would be good to re-introduce the volume microphone gain via the web gui (send volume) on the T4 series and the VP-530.

It appears that this was available on the T38 but not on the newer phones.

I know that increasing gain will affect sound quality and hence why it was removed but having no control over microphone send volume is difficult to work with.

It is changeable via auto-provisioning but would be better for it to be an option in the web gui.

If you could please add it to the Web Gui, that would be fantastic.