Support initializing generators with presets

[LogicalError]

If we detect which presets there are for a certain generator, we can show them in a dropdown. The user can then, at generation time, select a preset that sets all the values of the generator (even those potentially not visible at generation time) The size of the generator will then be overwritten after the preset is applied, while in generation mode This allows people to setup generators, including their materials, up front to ensure consistency & to quickly set the settings for lots of things that need to be created When no preset is used, the current selected material should be applied to all material slots