#12 PdfJs Viewer support for customizing the toolbar
  - Toolbar config is specified in model.toolbarItems, which can be
modified as needed by extensions
Ensure that Link button only appears and that keyboard shortcuts are only enabled on the document details page (ref. #27)
Remove CommonJS and AMD loading of spin.js - fixes #5
Restore transparent buttons when lightTheme is used, fixes #25
Remove 47px margin when the viewer is maximised in the film strip view
Increase toolbar height to 26px
Replace Maximize button with Present button for presentation file formats
New flat icons to match light theme. Ref. #25.