Filter by results map

[oliverroick]

Resolves #122

• Allows filtering the results by bbox of the map view
  • Add checkbox to enable the filter mode
  • extends usePaginatedResults with a state to hold the maps current bbox, and apply filter of the bbox is set
  • extends MapView so the bbox is set the filter mode is active
• Small design change: Make the map sticky, so it stays visible when scrolling through results
• Bug fix for locations without geometries: I noticed that we're receiving results for sites that have no geometries (contrary to what we initially assumed). I emailed Anthony and he said they are going to back fill the coordinates but it's best to handle this case.

[geohacker]

This works really great!