clean up meta.function identifiers about aquameta HOT 1 CLOSED

Casting meta_ids to string for use as URLs is straight forward except for function, where the argument type signature is part of the identifier.

PostgreSQL's function resolution procedure is here:

http://www.postgresql.org/docs/9.1/static/typeconv-func.html

The current version of endpoint.request just takes the first matching function with the same name and calls it:

https://github.com/aquametalabs/aquameta/blob/master/core/004-aquameta_endpoint/000-endpoint_server.sql#L708

We want to be able to use named arguments when they exist, ideally with a

endpoint.schema('bundle').function('foo', { name: 'Joe',  id: 'foo' });

This is nice, but it doesn't really match with the way PostgreSQL identifies functions. Functions can either have named arguments or unnamed, positional arguments. So we want to support positional arguments via an array as well:

endpoint.schema('bundle').function('foo', [ 1, 'Joe', 'hello' ]);

from aquameta.