Add bus-monitor convenience function

Simply dispatches to either audio-bus-monitor or control-bus-monitor 
depending on the rate of bus supplied as an argument.

Only accepts busses. If you wish to use numerical indexes to refer to 
busses, you need to use either audio-bus-monitor or control-bus-monitor
directly.
fix missing space
Update change log with more details of main release changes.
0.9.0-RC3