The triangle-ray intersection function used a hard coded epsilon,
which did not work for triangle meshes, that were either too small
or too large. Newly the epsilon may be provided to the AABBTreeIndirect
search functions externally and IndexedMesh calculates a suitable
epsilon on demand from an average triangle mesh edge length.
Fixed fatal bug with anchors for mini supports
Make the optimization cleaner in support generatior
Much better widening behaviour
Add an optimizer interface and the NLopt implementation into libslic3r
New optimizer based only on nlopt C interfase
Fix build and tests
