Other misc useful integrant helpers

A few things which seem potentially useful:

* `restart` - shorthand for `(suspend) (resume)` - skips the `refresh`
* `(find-component :k)` - shorthand for `(find-derived-1 integrant.repl.state/system :k)`.  Useful for defining REPL helpers like `(defn db [] (find-component :db))` instead of having to code against the specific implementation in use (which could change!)