Use a smaller map nav icon.

Replace 'PanZoomBar' with 'PanZoom'.  Plus a hack to make this work
for existing installs, ugh.

Fixes #514
Merge branch 'responsive' into smaller_map_zoom_nav
Merge pull request #549 from philipn/smaller_map_zoom_nav

Use a smaller map nav icon.
Fix search results with map on small screens

Fixes #554