Incentivize users to look backward

[shokiami]

Brief description of problem/feature

The goal is to further incentivize users to look backward while auditing. This is important for data quality because it is sometimes useful to see things from two different perspectives.

Current behavior

Recently, in #2860, I added the user's observed area to the GSV mini-map which will hopefully encourage the user to look around more thoroughly (i.e. the full 360 degrees).

Potential solution(s)

One suggestion @misaugstad made was to add an additional level to the fog-of-war for when an area has been looked at from both directions vs just one. Any other suggestions would also be greatly appreciated!