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
* Fix support heads floating in air
* Fix failing tests for the bridge mesh intersection
* Fix failing assertions
WIP refactoring support tree gen, as its a mess.
Completely remove the concept of CompactBridge.
Replace it with Heads having the same back radius as front radius.
Try to apply the same rules for mini supports as in the route_to_model step.
Increased accuracy of bridge_mesh_intersect shot from support points
Refining mini support integration
