[TW] Core/BG SOTA: Defense of the Ancients

- Move end of round spell to before defence to attacker team change
- Add end of round spell to also cast at end of the bg if relic is not
clicked
- Reset _gateDestroyed back to false during round 2 warmup
Merge pull request #29 from gecko32/TWBG

[TW] Core/BG SOTA: Defense of the Ancients
Merge branch 'master' of https://github.com/TrueWoW/TrinityCore into ghbb