Supported Furniture and More (0.5.14 Alpha)

This update brings a number of improvements for furniture in general, the biggest being that one can now make furniture require a supporting surface.  The next big thing is that you can now make furniture out of regular blocks, if desired.

In essence, furniture has four block types to choose from: fluid, occupied, platform and solid.  Fluid is disabled, by default.  You can now substitute any block for any of these in the furniture map, by using the following attributes in the furniture map:  "Define F", "Define O", "Define P" and "Define S".  Setting any of these to the name of a block substitutes that block when placing the furniture item.  Most furniture items use this to substitute an invisible furniture block that breaks when unsupported from below, so that their base must be supported from below.  If they're not supported while the simulation is running, they will immediately break and vanish.

There's also a new block-based tree item that's made purely of blocks, to demonstrate this feature in another way.

Last of all, I'm sorry for the long lack of updates.  I got sick several times and it was quite difficult to balance illness, work and this project all at once.  I'm doing better, though.  Hurray!