Feature/basic-euler-meshing

This MR contains the first working version of an Euler tetrahedral mesh generator. It will probably be changed quite a bit in time but this represents the underlying basis for the mesh generation code. Built on top the cadsystem (which is improved in this MR) merged previous it can generate invalid high-order tetrahedral meshes, the valid bit will come later with the linear elastic solver or similar strategy. As such it is not functional for end users so no user/developer guide documentation is included, just doxygen commenting. It is probably best to merge this now as it is already pretty big and waiting for the complete mesh generation pipeline will only add to this. Fixes and new features will be added in smaller chunks later. The code is implemented in an optional meshutils library that when activated compiles itself and the cadsystem.