Fix various indentation issues
Refactor decoration-related code

Split up ModApiMapgen::l_register_decoration()
Define and make use of CONTAINS() and ARRLEN() macros
Added names colours and refactored parseColorString()
Add option to enable mesh caching, add wallmounted for meshes.
Fix bug introduced by me (Zeno)
Check minetest.hud_change() parameters on conversion (Fix #1714)
mapgen: Resolve nodes in ctor rather than makeChunk
Fix uninitialized variable warning
Fix erroneous lua_pop parameter
Split up mapgen.cpp