Facia Config

This is the first version of loading the config from S3.

The changes in a nice list for you to read:
 - Loading all config.json files from S3 and subsequently loading each collection and each item.
 - Removal of configuredFrontsFacia
 - Upgrade of contentApiClient to 2.5-SNAPSHOT (So that we can use stringParams coming from a collection config) [More info](https://github.com/guardian/open-platform-content-api-scala-client/pull/20)

For now, most of the new code lives in FaciaAgent, apart from some of the models, which needed to go into common so they could be seen in the templates. I will begin to split this code out into the appropriate locations.