Algorithm/ants: performance fix

InternalGraph::SelectVertex now stores indices

Signed-off-by: Artem Plakunov <artacc@lvk.cs.msu.su>
Algorithm/ants: improved AntAlgorithm::BuildLink algorithm

Links are now assigned in a sequence corresponding to the sequence of
request element in the path.
Warning: it actually decreases the number of assigned requests. Further
research needed.

Signed-off-by: Artem Plakunov <artacc@lvk.cs.msu.su>
Algorithm/ants: performance fix

updateInternalHeuristic is no longer called when an element is removed
from the path while assigning virtual links (this was unnecessary)

Signed-off-by: Artem Plakunov <artacc@lvk.cs.msu.su>