switched off VS hosting for scriptcs.exe

This has annoyed me for ever and today VS blocked a git clean one time too many times so here, finally, is a PR to remove VS hosting.

> git clean -fxd
...
> Unlink of file 'src/ScriptCs/bin/Debug/scriptcs.vshost.exe' failed. Should I try again? (y/n)
:rage:

If anyone can cite a good reason for keeping VS hosting switched on please say so and I'll kill the PR but at the moment all I can see is a PITA with no benefit.