polygonal walls support and new border command

I added a border command to surround a selected region (cuboid and polygonal) with a border and I added support for walls on polygonal regions.

For both command it is checked if the selected polygonal region points are collinear. I found the method Vector2D.isCollinearWith but that didn't worked as expected. Maybe I was doing something wrong!?

I also needed to add an import for net.minecraft.server.v1_6_R3.Block to detect if a block is solid or not, to replace non solid blocks in border command (If you have grass on top of a dirt block it is replaced, otherwise for example the fence would be on top of the grass and that looks stupid.) Is there another way to detect if a block is solid without adding the import!?