bugfix: coordinate struct was inadvertently casting to int
First version of Prim's algorithm.
unordered_set requried c++11 support...
moved christofides parts to own header and source. Also continued on the beforementioned implementation.
Some cleanup.
Really bad integration of tabu search, yet it works. Also LocalSearch interface implemented. Also one fix that adds the last length back to origin as cost. Some minor refactoring