Imagery

- Article assets now look for a particular type of image (list view)
- ArticleTransformer now references Media Transformer
- New MediaTransformer for converting assets to the API required formed
- New global config file (covers all environments)
- New helper method to detect device - isTablet()
Merge branch 'CDN-Imagery' into dev-260714-0525
Bug fixes

- HomeResponseMaker: channels updated to fix with new DB content
- Removing channel ID from getArticlesWithEvents as now being passed
from HomeResponseMaker
- Updated channelId from WhatsOnResponder. Now passing ChannelId to
getEventsWithArticles
Merge branch 'Hot-fixes---channel-ID's' into MailChimp