Frontend: all blue background

Get rid of the tacky gradient on the banner.
Frontend: Format JSON now with null.

typeof null is 'object', which is all fine and dandy, but
it kinda messed up the presentation. Now we explicitly checks
for null if typeof is 'object', and simply print 'null' in that
case.
Fronted: Format fixes

  * Re-throw non-parse errors.
  * Set correct for all-expand-collapse button.
Frontend: Banner neater shadow

Make a more blurry shadow to give a more realistic
impression.
Frontend: Hash, let upload container clear floats