Plaid stone bricks, stairs, and a bit of cleanup

I consolidated the fluid and fluids packages... somehow I missed that I
had both, probably for weeks.  Added plaid stone bricks and stairs for
plaid stone bricks, plaid stone, plaid cobble, and plaid planks.  I
might end up editing the plaid plank render so they use the proper
texture instead of just the default icon, but, quite frankly, I'm not
sure how much I care about it.