Add test for nef::explode
Minor logging improvement

Add the function name to generated exception description.
Temp disable unused code to speed tests.
Add tests to expose non-manifold error at 90deg rotation.
Cleanup polyhedron::private

Move private impl into polyhedron and change assertion to throw as CGAL
basically only works in release mode and exception is better anyway - it
allows the cause to be tracked immediately.
Disable non-manifold test as investigation continues.
Refactor and disable non-manifold test.

Will be enabled later as investigation continues.
Merge branch 'master' of github.com:mythagel/cxxcam