Request: Plant Forest Worker Action

[AeonOfTime]

I just love spending the late game making my territory pretty by planting forests here and there, but that's one thing you cannot do in Civ 5 yet. I have no idea how complicated this would be to do as a mod, but I think it would be a great addition.

Beyond that, maybe some additional terraforming options would be nice, like razing or creating hills, turning tundra into plains...