LiveSplitImageSource: Get rid of obsoleted ApartmentManager property usage

It is indicated on the ApartmentManager page here:
http://msdn.microsoft.com/en-us/library/system.threading.thread.apartmentstate%28v=vs.100%29.aspx
Merge pull request #48 from lioncash/threads

LiveSplitImageSource: Get rid of obsoleted ApartmentManager property usage