Squashed 'Extern/LuaBridge/' changes from 74101d4..a34416f

a34416f Added tostring member to LuaRef
ee427df Added LuaRef_cast for convenience
06f3640 Pass by const reference for primitive & container types
f95eff9 Use *integer() Lua routines for integral Stack conversions

git-subtree-dir: Extern/LuaBridge
git-subtree-split: a34416f2f332fde0753f632cd761e7d83613c746
Merge commit 'a4fdbd7cc1fec33524b43f4eccc1d1fafbe2a6dd' into develop

Conflicts:
	Extern/LuaBridge/Source/LuaBridge/detail/Stack.h
Fix whitespace and style