Add onPageDescription, imageUrl, imageWidth, imageHeight,
isImageDisplayed to Front
Add id and collectionType to CollectionJson
Add empty to Config
Add emptyConfig to CollectionJson
Add apply for CollectionJson with default parameters
Remove id from CollectionConfig
Call apply withDefaults
Fix empty
Merge branch 'new-front-fields'

Conflicts:
	src/main/scala/com/gu/facia/client/models/Config.scala