How can I use the new foliage features in 4.7?
Is there any documentation on it yet or can anyone show me how?
I’m interested in the new per-instance LOD support and per-pixel dithered LOD transitions
And of course the new two-sided foliage lighting
How can I use these 3?
For the two-sided foliage lighting you just have to choose “two sided lighting…” as a blendmode + connect the texture with the subsurface link (you can controle the subsurface strenght with a multiply + a constant vector). Everything else is the same as in a ordinary material 
This is used by default with any kind of instanced meshes. So all you need to do is placing your meshes with the foliage tool.