Hygiene: Change image viewer route

Change #image-[image] to #image/[image], similarly to what other
frameworks use (e.g. Backbone). This was previously impossible due to
bugs in History.js which we no longer use.

Change-Id: If2c1951bba50da719c6cae55c9e0abb8d5067e71
Merge "Hygiene: Change image viewer route"