Show search facets along the left side of the results page. Clicking on
a facet re-runs the current search with the new facet appeneded.
Selected facets are styled to indicate they are selected. Clicking on a
selected facet removes that facet from the set of selected facets (i.e.
it backs out the facet).
TODO: update CSS to match default Evergreen skin
Signed-off-by: Bill Erickson <berick@esilibrary.com> Signed-off-by: Dan Scott <dscott@laurentian.ca>