Merged bug fix mentioned in http://casparcg.com/forum/viewtopic.php?f=3&t=2480

Previously AMCP commands split into multiple TCP packets where not correctly parsed.
Fixed bug where CG INVOKE no longer works in cg_producer.
#252
Support for CG PLAY was missing.
#281
Added support for iVGA consumer to not provide channel sync even though connected. Useful for iVGA clients that downloads as fast as possible instead of in frame-rate pace, like Wirecast.
<provide-sync>false</provide-sync> has to be added inside the <newtek-ivga /> element to not provide channel sync when connected.