Custom Tree Mod Element Types

Issue description

1.8.3 adds new trees type, that's cool! but there is a problem, What I was expecting in 1.8.3 is that these trees types are made with our custom blocks, but it's only tree types with vanilla blocks, so am a bit sad :( For 1.8.4 can make custom blocks using these types of trees?

PS: Between there is dark oak trees missing

Issue comments

We have added all tree types that can be directly referenced AFAIK.

We will consider adding tree types to custom trees too, but most likely not in 1.8.4 as the feature list for 1.8.4 is quite large already.

I think I have an idea of how to do this without waiting till a lot of versions of MCreator only using new 1.8.3 block features  

Will this include a sapling and options for 2*2 and 3*3 variants? Along with choosing both the minimum and maximum height of the tree.