Add a MST-based auto-clustering container and implement a PoC for autodetection of bases and outposts.
Cleanup and improve clustering and disjoint sets code.

In particular, use insert instead of emplace with unordered_map and multimap
for compat.
Move clustering code in the gamelogic.
Make use of MoveTowardsRoom for base clustering beacons.
Use namespace instead of singleton scheme for base clustering.
Don't automatically tag OM/RC as its location can be infered from the main base beacon.
Merge pull request #328 from Unvanquished/beacons+clustering

Add a MST-based auto-clustering container and implement a PoC for autode...