mesh LOD - WIP
Merge branch 'master' of github.com:nem0/LumixEngine into mesh_lod
refactor
LODs are loaded from a model file
removed unused class
fixed crash when there is a renderable w/o a mesh
refactor : removed Resource::getReadCallback
refactor: allocator always the last as a function's argument - closes #374
Merge pull request #384 from nem0/mesh_lod

Mesh lod