action (prove it) – gallery updates

[mmwtsn]

1. If the campaign does not have any report back images associated with it, a single fallback image without pagination is displayed.
   
2. Pagination icons are now pulled in using our icon font.
   
3. Markup cleaned up.

Closes #828
Closes #829

[DFurnes]

We should probably leave some TODO comments next to any placeholder images we're using so that they don't get lost. Otherwise all good. +1

[DFurnes]

Also, looked like there was a bunch of re-indenting in the template? Just worth a double-check to make sure that was the case.

[mmwtsn]

@TODO flags added! The indentation issue was simply Git having trouble with the diff. That commit removed a wrapping div and indented all previously nested code.