document up-to-date gmoc-db schema and supported metrics in a permanent place

[chaos@bbn.com]

For GEC14, the gmoc-db database schema was placed at:

http://groups.geni.net/geni/attachment/wiki/GENIMetaOps/gmocv3.rng

and the list of supported monitoring metrics was placed at:

http://groups.geni.net/geni/wiki/GENIMetaOps/DraftMonitoringMetrics

Find permanent homes for these two pieces of information to be documented, ideally where it's easy to keep them up-to-date.

[chaos@bbn.com]

Again, this is not a time-critical task, and certainly it should be done after a code revamp rather than before. I'm just making a ticket so we don't forget to update the documentation, and revisit URLs and auto-updating docs if feasible.