Persist vines

[Maxopoly]

We might want to use that as XP ingredient, so we should persist it.

[benjajaja]

And generally control in what conditions they grow (biome, light, surface), and how fast.

Currently vines grow downwards as long as they are unobstructed. They are used this way as decoration, which is probably irrelevant here. Whether used as deco or as farm, the important point is: the "source" vine gets placed, and then is never removed. RB is designed so that a plant is no longer tracked and removed from the DB once it is fully grown.
Except fruitful plants and cacti, which if planted in an autofarm, are in practice ever-persistent since they get re-added and tracked right after they grow to completion and are auto-harvested.

So I suggest to let RB grow vines until they hit an obstruction, then stop tracking it. If they get trimmed (blockbreakevent on a vine) then recalculate growth stage of source and start tracking again if needed. This way they will behave as expected by players.
This would have to be handled as special case in some parts of the code, since RB assumes a maximum growth stage for plants, but that isn't really applicable to vines.