Co-authored-by: supermerill <merill@free.fr>
Based on the unfinished idea of @supermerill, defining ExtrusionRole
as a bit mask of ExtrusionRoleModifier.
Because the ExtrusionRole was used for both ExtrusionEntity and
G-code export / G-code viewer, the original ExtrusionRole had to be split
to ExtrusionRole and GCodeExtrusionRole to support bitmask attributes
for the former while keeing a low number of ordinary values for the latter.
producing better shortest path estimate than the "closest next neighbor"
heuristics. The new greedy algorithm utilizes KD tree for closest
end point search, and builds a graph to detect loops.
PerimeterGenerator newly uses the optimized TSP algorithm.
ExtrusionEntity has been refactored / simplified.
Iterator loops replaced with C++11 loops.
Fixed clone() methods to return an ExtrusionEntity*.
PerimeterGenerator now uses move semantics on ExtrusionEntity a little
bit more.
