Prototype Resource Query API (/find)

[MikaelSmith]

Add a /find endpoint that implements selecting a set of entries based on a predicate query language. This should become the intermediate format used to implement queries from the find command, with predicate matching moved to the server.

Detailed spec to be added later.

[ekinanp]

Future work could remove fullmeta and have the schema figure out which metadata to use. For example, given something like

find -m .tags

we'd get tags as the parsed key. Logic would then be:

• If tags is valid key sequence in partial metadata schema, then use that. Otherwise, if tags is a valid key sequence in full metadata schema, use that. Otherwise, it is an invalid key sequence.

[ekinanp]

We'll also need to document this stuff on the website, least the RQL grammar in detail.