[MonoDevelop] Changes in the Stetic add-in

[Lluis Sanchez]

Hi,

I've done some important changes in the Stetic API which will allow
running the designer backend in a separate process. The end goal is to
be able to reload assemblies in the designer without having to restart
MonoDevelop. This is not stable enough to be usable, but at least the
needed API reorganization is now done (the new API supports in-process
and out-of-process modes).

This change may introduce new bugs and unstabilize a bit the MD designer
add-in. I'll try to fix any problem that may arise ASAP.

Lluis.