Remove `idField` from spec

Structural descriptors are OOB information that _are not_ part of a `Qo`. To act on specific fields, use matching constraints
Place `offset` and `limit` in root Qo
Minor documentation clarification for .resource
Convert `identifiers` to `ids`

Needlessly verbose descriptor
Change `fields` and `excludeFields` and `include` and `exclude`

Unify the whitelist + blacklist naming convention
Remove `rename` modifier type
Rename `modifiers` to `updates`
Rename `constraints` to `match`
Rename `order` to `sort`, as array of strings
Rename `content` to `body`
Add RFC2119 style SHOULD, MUST, etc definitions
Release 0.3.0