Ergonomic improvements for querying

[richfitz]

As discussed by Jeff in #156 and elsewhere (#154, offline), it is hard to know what to put into functions that might interact with metadata on remotes. This PR starts the process of improving this.

• If the user specifies a location (non-NULL argument location), then allow_remote should default to TRUE. I've implemented this by changing the advertised default to NULL and evaluating it after seeing what we were given for location.
• The arguments to compose a query (expr, name, etc) would be useful on user-facing functions for autocomplete etc. Otherwise they are several levels of man page away and really quite hard to find

The improvements continue in the more disruptive PR #187

[M-Kusumgar]

Small suggestion but yh i think this is in the right direction based on memory of conversation with jeff, the orderly search documentation improvement is also much clearer thanks