PA control enhancements

Updated PAObj and pa_control to allow for a mix of different zone types and added a new zone type of "object". You can now use an existing object as a PA zone or a member of a group if it accepts ON and OFF commands via set. I tested this by using an Insteon object.

This could be used to turn on a device or lamp while MH is speaking. Perhaps an animated head just for fun! More practically, an IOLINC could be used to turn on a remote speaker. Scenes should work as well.

The on thing that I'm not sure how to handle long term is the extra delay in turning things on when there are multiple devices to send commands to. There could be X10, Insteon, weeder and other devices that are all sent messages. The io device, amp or whatever should confirm that they're on before the audio is sent, or we may miss the first part if the PLM is busy. Either way, this is a step in the right direction.