Resolve "Greedy Packing"

Closes #7

See merge request !8

Merge branch '7-greedy-packing' of gitlab.informatik.hu-berlin.de:scherzej/psco-2019-gp into 7-greedy-packing

Optimize performance of partition

See merge request !6

Add branching after degree of nodes

See merge request !3

Incremental bfs

See merge request !7

# Conflicts:
#   bnb/graph.cpp
#   include/gp-bnb/graph.hpp
#   test/edmonds_karp_test.cpp