Improve refinement rules

[dengwirda]

Revisit rDT refinement rules:

1. Refine boundary facets until their nodes span a common boundary contour. Such contours should be pre-processed from the geometry, being either: topologically disconnected, (piecewise) separated by sharp features, or by different IDtags. Perhaps other things too?

2. Support interior mesh selection by reachability to user-defined seed points, as well as current in-polyhedron strategy.

3. Support meshing of domains defined by (even more) inconsistent geometries: especially those that have not been properly intersected, etc.