[Enhancement] Set seed for density functions, noise setting generators, etc

[stedwesd]

In all generators that visually display your generators in any way (e.g. Density Function, Noise, etc ), you currently only have the option to generate a new seed, but cannot see what seed is used specifically or change it.

Being able to set the seed manually would be useful for multiple reasons, e.g. comparison of multiple worldgen elements that rely on each other, or the ability to reproduce the result in game (and vice versa).