Render places where tree was, but is missing (and not a stump) and there is no tree in it's place

[Gregory108]

state=gone category now holds 2 meanings:

1. error input, tests, and other irrelevant data points, aka "garbage"
2. tree was there, but was removed (including a stump), but no tree was planted in its stead

The later should be displayed, because we collect those empty places as they are actionable. I suggest black semi-transparent square (because, mostly those are dirt squares))

However, when something, eventually, will be planted in this place, it should stop being visible, because the empty place it was filled.
(But, of cause, the story of a tree that was there should not be deleted)

• add graphic element for points state=gone points
• clean production DB from "garbage" (regularly)
• add "do not show if there is a tree that replaced it" logic

[umonkey]

@Gregory108 you can actually see "gone" trees if you type "all" in the search bar. Displaying them by default could be a little misleading, as you expect a map of trees, not a map of places where trees once were, and colors cannot be intuitive, so this puts extra pressure on new users.

[umonkey]

@Gregory108 another thing with rendering "gone" is that they are (hopefully) replaced with real trees at some point, and would overlap on the map. So we'll probably need to add a new status "replaced", to finally hide the dot, as soon as at least one tree gets replaced.