write a sample ACL policy for the GENI relational object model

[chaos@bbn.com]

Between now and GEC17, we'd like to modify the various tools which allow access to gmoc-db relational data, to enforce ACLs for who can see which pieces of data.

Write up an example data download policy covering who can access each piece of data in the GENI relational model, either as part of the general relational model documentation, or as a separate file.

Note: this data download policy is an example implementation which we'll use in defining what work needs to be done on download tools. It is not intended to be the canonical download policy for GENI relational data.