Persist filtering when navigating pages

When moving from the main aggregation page to a specific aggregation
page, the filters are kept and also now updated in the left hand column.
Unfortunately, these filters are lost when returning to the main page,
or going to an individual item page, but for now this is probably ok.
Bar graph links now also have filter args
Expand left pane if filter exists on page load
A couple of bar graph changes

Changed margin.
Also bar graph now shrinks if less than 6 items.
Merge pull request #105 from dannybutler/master

Filter persisting changes