only re-highlight the portal if the highlighter is active
fix 'captured' being set when it should have been 'visited' for link-related messages
fix crash when the selected portal is not in the map data (e.g. while loading), when the highlighter is selected
uniques plugin: better syncing between the data and the state of the highlighters. sync case included, but not tested yet...
uniques plugin: change the highlight colours
- red: not visited/captured
- yellow: visited, but not captured
- no highlight: both visited and captured
simpilfy highlighter registration
uniques: extract highlighter