Feature/cadsystem

This brings in three classes that act as a wrapper for opencascade to allow the loading and querying of cad information form STEP and IGES files. The CADSystem class loads and process the cad file before creating two maps of the classes CADCurve and CADSurf which contain the individual opencascade entities from the CAD file and querying functions.

Because opencascade is such a huge set of libraries with many active versions, all of which can be compiled in numerous different ways. Cmake has been set up to download known working precompiled versions of opencascade dependant on the operating system, it then unpacks the libraries and headers into TPDIST to ensure they are included in the install step.