Core/MMAPs: Add support for raycast

Add an optional parameter "straightLine" to PathGenerator::CalculatePath() which will use raycast instead of path finding and will return only complete path from start to end position.
Implement this new type of path in SPELL_EFFECT_CHARGE , fixing strange behaviors when using Charge with mmaps enabled.
Merge branch 'master' of https://github.com/TrinityCore/TrinityCore into ghbb
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