* Factor out the post navbar into a component. The post navbar is the
part of the post containing the current search, the list of pools, and
the list of favgroups, along with next/prev navigation links.
* Change navbar markup: remove various unused CSS classes/IDs, change
pools to use same markup as favgroups, replace nested <div>'s with
flat <ul>/<li> list.
* Use CSS to truncate long searches/pool names/favgroup names if they're
too wide for the screen (especially on mobile).
