DB/Conditions: Healing the Lake/Neutralizing Agent

By MitchesD, closes #3337
SQL: Sync auth_database
DB/Conditions: Fix conditions for spell "Symbol of Life"
SQL: Renamed updates to follow naming convention
Core/Skills: Check if a skill can be unlearned with SkillRaceClassInfo.dbc data and use max skill level from SkillTiers.dbc
Tools/MMapsGenerator: Improve mmaps generation time on multi-core CPUs

Queue biggest maps first for mmaps generation to avoid waiting for last map, usually map id 571.
Fix wrong maps count being printed on startup.
Core/MMAPs: Update recast

Update recast to https://github.com/memononen/recastnavigation/commit/42b96b7306d39bb7680ddb0f89d480a8296c83ff
Previous MMAPs might still work but it's recommended to re-extract them.
DB/Quest: Redemption

Fix missing delete.
Core/Items: Items shouldn't have a negative item level

Closes #11631
DB/Quest: A Suitable Disguise

Original Work by Discover-, fixes by Nastrand, zaphod77, foldy and, dr-j.
Closes #3291
DB/Spawns: Add multiple Brewfest missing things

By Discover-, updates #3619
Core/Spells: Fixed professions resetting back to 1 when learning new level (expert/artisan)
Core/Loot: Skinning improvements

* Set skinnable flag only after all loot was taken
* Creatures are skinnable only once - after skinning, the player only has to loot the creature again if he did not take all skinning loot
Scripts/MagistersTerrace: reworked InstanceScript and fixed some issues on boss Vexallus
* removed old hacks and added missing auras
* Vexallus converted to EventMap
Merge pull request #12364 from MitchesD/misc_2

Scripts/MagistersTerrace: reworked InstanceScript and fixed some issues ...
Core: Fix warnings and kill again whitespace ...
Core/Mail: Fix exploit that allowed to send free emails
Script/MagistersTerrace: Fix fail in 27f28552489bab153d5c4717ce48e31496b4c43f
Core/Misc: Define CREATURE_TYPEFLAGS_PROJECTILE_COLLISION
Core/Spells: Ensure Haunt's healing takes in consideration crit damage