Core/Instances: Fix Instance binding

Fix players not being bound to instance if the group was disbanded before killing any boss.
Fixes #437
Scripts/Halion: Fixed Soul Consumption's pull effect.

Thanks to Winterfell for pointing out the issue.
Core/Entities: correct creature damage, offhand damage should work too
* todo: some creatures need dmg_multiplier update in creature_template
DB/Spells: remove duplicate/invalid entries from spelldifficulty_dbc
* For new entries: use spellid0 as id to avoid conflicts with dbc file
DB/Spells: correct more spelldifficulty_dbc entries
* add log message to find wrong entries
Core/Threading: Handle CMSG_ZONEUPDATE only in WorldSession update - changing zones triggers changing chat channels, what is not a thread safe operation
Scripts/HoS: update Maiden of Grief
Core/Movement: Fixed vehicle passengers disappearing clientside

Closes #11411
Misc:

* Tools: Fixed a compile warning
* Commands: Fixed npcflag format in .npc info
Core/Entities: add some log messages in CheckCreatureTemplate
* Happy Error Spam
DB: update some creature templates
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore