MixMonitor parameters for B() option

[jahoppe]

The MixMonitor application has the B(x) option that will play a beep every x seconds during the call recording.
Please add the following parameters to B():
"filename" - the audio file name to play instead of the standard "beep" file.
"volume change" - Integer that can be negative, that adjusts the volume of the beep or audio in the "filename"

Finally, allow the "filename" or beep to be part of the recording. This gives proof that the beep or "filename" was played.