Remove Rhinocommon from core and test projects.

* Rhino support to be re-added (to PlanktonGh) in next commit
* Vertex position stored in component form (X,Y,Z)
* PlanktonXYZ will handle point/vector representation
* A couple of PlanktonFaceList methods renamed (more Rhino-ish)
    * FaceCentroid -> GetFaceCenter
    * GetVertices -> GetFaceVertices
* Smoothed off some rough edges
Re-add Rhino support

* Contained within Grasshopper project
* Implemented as extension methods (fully integrated)
* Not yet tested in Grasshopper
Re-add old method names for backwards compatibility

* marked as obsolete
* remove before version 1.0.0
Update Rhino support extensions

* fix bug where Grasshopper wouldn't load RhinoSupport class if it only had extension methods in it
* add some simple extensions to create point/vector from plankton vertex/vector