Only start history once

We used to call Backbone.history.start() every time the user changed the
version they were looking at. Make sure to only call it the very first
time.
Don't show a trailing comma in the related functions list
Smarter search result filtering

Since we want 'function' results to override argline results, let's not
even search for them if we've found it in the function name, which means
less work during the search and display phases, as we don't need to
filter these results out either.