Add a /status endpoint for NodeNorm ES

[gaurav]

I set it up a /status endpoint for NodeNorm (e.g. https://nodenormalization-sri.renci.org/status) to provide some information about memory usage and database information, but the babel_version and babel_version_url fields are really useful for users to figure out what the Babel version is (so they know when to invalidate their cache). Would it be possible for NodeNorm ES to return their information, either in its normalization results or as its own endpoint?