Draft: Change the structure of the repository

The Imstk folder is intended to be a subfolder of a project This way an imstk package can easier be created and used or The imstk-unity repository can just be checked into a unity project

This mirrors the structure that pulse uses https://gitlab.kitware.com/physiology/unity the asset is then created from the subfolder that contains all our data

Also replaced the swig generated swig files with the compiled C# dll

Fixed a small bug that caused an error message to be shown when no haptic device was attached (null reference)