Feature request: Add support of alpha transform

[Adolio]

Alpha property "@A" of object tag is currently not parsed and not handled in Transform class.

[Adolio]

For further information: http://www.brashmonkey.com/ScmlDocs/ScmlReference.html

[wastedabuser]

@aureliendc, this should be a really straightforward implementation. I can help you. Unfortunately, as i see currently @SammyJoeOsborne has no interest in improving SpriterMC :(

[wastedabuser]

I have implemented the "@A" property