Reorganized repo and renamed schema files according to conventions spelled out in the readme.
Replaced voxels-metadata-schema with the more complete version copied from janelia-flyem/dvid-api
schemas: dvid-voxels-metadata: Allow empty string for resolution.
schemas: Added a "version" field to all schemas and a corresponding verison field in the schema properties itself.
When locating a schema to validate with, use the new directory structure of the dvidschemas repo.
Trying to fix subtree. Merge subtree onto the master branch.
Merge commit '759e5baa3a6beac0039c41892c3d506ab25adcff'