A range of new features and fixes #2

Features:
- uploads can be set up to go through http://filepicker.io given an API key
- preview images can be viewed in a window filling viewer overlay and viewed as a slideshow
datasets can have a fully customisable view associated with them

Fixes:
- Datafiles are now sorted consistently in list. The list is always loaded via ajax now
- moved a logging statement that seemed to cause errors