Add fdsn-datacenter.json for harvesting
Closes #21 (closed) by creating new release.
The FDSN has created a data center registry: http://www.fdsn.org/datacenters/ which is a simple registry of seismological service operators, specifically web services compatible with the FDSN's specifications. In this registry, a data center creates and controls their own entry. More information about the management of the entry is here: http://www.fdsn.org/datacenters/help/#registry-management
The information provided through the registry allows seismologists (and others of course) to find the web services offered by a data center, how to cite usage of the data center, contact information and a bit more.
The json file in this merge request will be set up to be "harvested" to manage our data center registry information. Harvesting allows us to version changes to our metadata, and the web form does not support metadata without datasets (which are not a good fit since ComCat is multiple fdsn network codes).