Buckets!

This adds the notion of buckets to poky alongside a few other changes and fixes.

-   Update schema to include bucket varchar
    -   Add `created_at` and `modified_at` timestamps (TODO add update trigger)
-   Update KeyValueProtocol to include bucket paramter before key
-   Remove RDMSKeyValueStore protocol, it was an uneeded abstraction
-   Remove unused `poky.kv.jdbc.pg-json`
-   Move `poky.kv.jdbc.text` to `poky.kv.jdbc`; will update
    `poky.protocol.**.text` namespaces too
-   Fix jdbc mget; parens weren't correct & didn't generate k-v pairs
-   Make the `S` & `M` servers in `repl_helper` delay objects to prevent instantiation while parsing/evaluating. They depend on environment variable `DATABASE_URL` and caused `lein check` to fail if it wasn't set.
-   Various trailing whitespace cleanup