Fixed bug where protocol splitting didn't require :// but any of :, / or /
Return by const reference instead of by value in parameters class.
Made ffmpeg producer output relative path (to media folder) via OSC instead of absolute path
Experimental support for switching output between premultiplied / straight alpha

Use
MIXER 1 STRAIGHT_ALPHA_OUTPUT 1
to turn on straight alpha output on channel 1 or configure it in casparcg.config under the <straight-alpha-output /> element for the channel

The default is to not use straight alpha output

#50
Merge branch 'master' into master-vcexpress