Included "mscorpol" as a git submodule.

Hi Eskil, I forked your lofar-lb repo and added the mscorpol package as a git submodule. This way you can get the latest changes directly from my mscorpol repo. It's in a branch called add_mscorpol_sub so you call pull it, merge it, and push it in lofar-lb now.