Merge pull request #9280 from horn/summons

Core/Summons: Implement summon groups system to be able to summon multiple NPCs at once without need of hardcoding the positions. Almost all hardcoded positions can now be moved to DB.
Core: Fix a comment in LoadConfigSettings

Closes #9292
Script/Quest: The Lonesome Watcher (12877)

Closes: #9185
See: http://www.youtube.com/watch?v=ylZRMu9CIMw
Script/Commands: Make creature_summon_groups table reloadable.