graphics error logging (turanszkij#999)

skip a bit of unnecessary work in some cases

dds fixes for npot textures

vulkan: disable mesh shader because AMD can crash when compiling a sh…

…ader, without any error report

added texture.IsValid() lua binding

gpu optimizations

some improvements

custom shader fix

improvement for streaming mipmap feedback

FBX importer: override file callbacks to correctly handle UWP