Add Text object that wraps new textimpl module.

textimpl uses cairo to create a text path, but conversion
to OCC isn't implemented yet.
Add (slightly broken) cairo-to-occ implementation
Add closing edge on cairo close_path.
Factor out some functions from cairoPathToOccWires().
Move current point to end of curve after cairo curve_to.
Fix handling of cairo sub-path start points.
Invert y direction before getting cairo text path.
Correctly convert cairo curves to Bézier curves, not B-splines.
Refactor creation of compound from text faces to makeCompound().
Group text wires into faces, so inner loops are treated as holes.
Replace use of IntTools_FClass2d with slightly simpler BRepClass_FClassifier.