Core/PacketIO: Corrected structures of SMSG_PARTY_MEMBER_STATS and SMSG_PARTY_MEMBER_STATS_FULL, fixes weird pet behavior in groups (appearing as "Unknown", breaking combat logs)

Closes #345
Core/Spells: Fixed a silly typo in SpellInfo::_IsPositiveEffect.

Fixes some auras being displayed as debuffs while they should not. (Just see Invisibility #66)

Ref. #7912
Core/Spells: Fix a logging message error
Merge commit '26efbacfab68e392d18d0b4fd66cb400660605b6'
Merge branch 'master' of https://github.com/wkoot/TrinityCore