Area filling options:  wireframe, partial, full..
* implemented as css classes on surface element
* patterned fills can be done with css too.. removed the
  code from areas.js to set patterned fill on each element)
* dummy test code in `map_data.js` uses 'w' key to toggle..
Add area fill selector (wireframe/partial/full) to map data panel
also:
* style dark tooltips with shortcut keys
* use uppercase for shortcut keys