Create WidgetBannerSelector and add banner images
mount /widgets into main sitemap
Implement /widgets/resource redirect
Cleanup in widgets

- Removed unnecessary pipeline types
Refactoring WidgetBannerSelector to take identifier as the selector expression
Merge branch 'dryad-master' into trello-13
Disable banners for items in workflow/workspace
Should handle article DOIs instead of package DOIs
Refactored widget lookup into base class, since it is used by banner and redirection
Rewrote resource handler as an Action

Uses WidgetbannerLookup to get data package DOI from article DOI, and redirects user to data package page
Merge remote-tracking branch 'origin/trello-13' into dryad-master