[FR] Add option to disable solid layer under support

[unlimitedbacon]

This request comes from a customer. it's not a major problem, but it would be nice to have.

I have below a screenshot of the first layer of the part I am trying to print. The first layer of support material has a solid infill as seen below. Instead of this solid layer of support material I am trying to make the first layer a grid with maybe 15% infill like the rest of the support material, but I cannot seem to find a setting that does this for me. Since the first layer speed is only 15mm/s I have found this layer to entirely too much time. I feel bad for saying this, but I had to use Cura to get a G-code that would be ≈3 hours instead of 7 hours simply for that reason alone.