Tidying project compilation & ignore bin/debug

ILRepack is now included as a managed package
When compiling the project it:
- packages all binary files into a single .gha file using ILRepack and
moves it to the Grasshopper plugin library  (note: uses a hard-coded
path to plugin directory so is brittle)
- No longer attempts to register as a COM object
- Checks for integer overflow
- Does not attempt to open Rhino.

The bin and obj folders have been added to the gitignore.