Tidy up (whitespace changes only)

Just tidied up PlanktonMesh.cs (well, SharpDevelop did...) while I was working on it. Figured I should commit the whitespace changes first to avoid muddying the waters in the next commit.
Create PlanktonMesh from face-vertex representation

* new AddFace method follows the process described in OpenMesh's PolyConnectivity class
* Handles creation of any missing halfedge pairs and ensures halfedge data structure (HDS) is always correctly linked (next/prev/etc.)
Add test project