Refactor config: use resource where appropriate

Avoids having to look it up again in the app configuration.
Add support for nested schemas in parameter table

If the field defines a schema, add any fields from the nested schema
prefixed by the field name.
Add support for nested key schemas

If the field defines a key schema, add any fields from the nested
schema prefixed by the field name and a * to denote the wildcard.

See also: https://github.com/nicolaiarocci/cerberus/pull/36
Merge pull request #9 from kynan/nested-schemas

Add support for nested schemas in parameter tables