Add Stars overlay

[zbycz]

It should be very easy to do, and very useful.

Overlay layer should be possible to turn off in LayersSwitcher.

Icon could be star-11

[waldyrious]

I'm a bit out of the loop here — what does "stars" refer to in the context of this issue? User reviews? Actual astronomical stars? Something else? :thinking:

[Dlurak]

Users can mark features as stars, they are basically favorites.

The right of these three buttons can be used to mark a feature as a star.

I hope that helps :)