Scripthost cleanup

Fixes (or I hope it does) #460 and #446.

there is still compilation problem (#448) so for now this only works as `scriptcs <script> -inmemory` but I tested against Web Api, SS and Nancy script packs and they all work even though some of them pull the old contracts (0.3.2)

I'd suggest you pull this branch and try to run the script packs too.