Added new mcstas loader. re #8194

Provided by Torben Nielsen. Here modified to adjust names of workspaces added to workspace group
Merge branch 'feature/8194_mcstas' into develop. re #8194

Conflicts:
	Code/Mantid/Framework/DataHandling/CMakeLists.txt

It looks like LoadMaskingFile has been removed recently from development branch which appear to have caused this conflict