Replace "Alien base" and "Human base" beacons with "Base" and "Enemy base".
Implement outpost beacons.
Fix a spelling error in cbeaconPersistent_t.
Make BCT_BASE* and BCT_OUTPOST* beacons disappear if there are no buildings in their vicinity. Furthermore, prevent placing these beacons away from bases and outposts.
Merge branch 'beacons' of https://github.com/Unvanquished/Unvanquished into beacons