Adds support for config of additional helpers

Extends the dustjs helper registration with adaro to support configuration of each module if necessary. This allows more sophisticated helpers to bring in their configuration from the main file without odd workarounds. The configuration format looks much like other module definitions in the Kraken environment.
I'm not certain what the best name is for the `arguments` bit, as it isn't quite the same as the typical meddleware config. `options` may be more appropriate.