Allow adding F&F indicators as circle overlay on country maps

[tmfrnz]

finishing tasks

• [x] fix multi-layer tooltip
• [x] add unselect X
• [x] add link to indicator
  • [ ] ideally as modal
• [x] store and read selected indicator in/from URL
• [x] circles don't scale to 100% for percentage data on overview maps
• [x] make sure we store indicator in bookmark (and other recent settings)
• [ ] panels should close on country select on map

nice to have

• [x] consider showing description in tooltip (w/ click to navigate/open modal)
• [ ] do not zoom to bounds on ff-indicator change
• [ ] remove unit from title-link of selected indicator and move above the link
• [ ] group option list by resource as on f&f overview
• [ ] consider adding GDP and population from country table
• [ ] add option to minimize panel
• [ ] improve tabs
  • [ ] show if F&F has indicator selected
  • [ ] add "key preview" icon
• [ ] consider adding unit to options in select list
• [ ] consider way to indicate no data value, ie red circle
• [ ] consider option to show percentage data differently e.g. as colored area instead of circles
  • [x] or at least set maxValue = 100%