Feat: Added numlevels parameter to render datasource.
Feat: Added numlevels parameter to render datasource.

Allows the user to disable computing a levels hierarchy for projects that do not have generated mipmaps.

seung-lab/neuroglancer,janelia-flyem/neuroglancer,google/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,google/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer,janelia-flyem/neuroglancer,seung-lab/neuroglancer,google/neuroglancer,google/neuroglancer,janelia-flyem/neuroglancer