Support aliases for schema and field names

[machristie]

To allow schema and field names to evolve without breaking API level SQL queries, the API should support adding aliases for schema and field names.

[machristie]

Another idea that came up recently, we might want to support linking metadata schema fields. So for example, there might be two schemas that each define a field slightly differently but they both represent the same thing. One use for this would be to create a common metadata schema that links together the fields across more specific metadata schemas. Queries against the common metadata schema could then return results when matching fields in those more specific metadata schemas.

Essentially this comes down to a question of whether API users should define their own common metadata schema when metadata comes from multiple sources and then pre-process metadata to adhere to their common metadata schema. Or, they could leave the metadata as it is from each source and link together fields.