* Move documentation from `ns` into `defprotocol` and the method
declarations.
* Indicate which protocols may be extended via metadata
(`SettableParameter` and `Sourceable`).
* Remove `execute!` and `execute-one!` from `result-set`.
* Add `-execute-all` and `-execute-one` to the `Executable` protocol
instead.
* Remove `:row-fn` support.
* Allow a `PreparedStatement` to be `Connectable` so it can be used with
`datafy`/`nav`.
* Rewrite `RowBuilder` protocol and add `ResultSetBuilder` protocol; add
`as-arrays` as a builder.
