Make sure PUT voxel requests group goroutines together
First-pass merge support for labels64 and additional fixes
Consolidate HTTP API call handling to server package
Merge branch 'master' of github.com:janelia-flyem/dvid
Update ROI test for simple mod
Second-pass labels64 merge work.  Still require denormalization of label POST.
Fix ROI ptquery bug and add more ROI tuple tests
Fix large volume indexing.  Fix merge denormalization.  Add labels64 POST denormalization.