Merge pull request #232 from Foereaper/Rel20

Added base for BG methods, filter for Lua engine files
[Deps] Fix Linux build. Thanks zackbcom
Documenting and Optimizing DBCStores related functions.

- Adding documentation of DBCStructure.h.
- Removal of unused variable of structure (avoid loading them).
- Removal of unused structures.
Merge pull request #236 from Warkdev/Rel20

Documenting and Optimizing DBCStores related functions.
Update submodule