Raise a building on a held plot

Building is the first pillar of the game (#77). In the economy (#121) a plot is held by locked stake, but the right to build is only recorded. The alpha needs the first real step: your own house in a town.

• Commission a building for your plot from the generator (uo-buildings: a kind and size that fit the plot, a few variants to pick from) and pay for it in materials delivered to the site: stone, boards, ingots, glass. This is the main demand for gathered goods.
• Construction takes time and shows stages; the finished building enters the world as server statics (patches over the baked world, like other object changes).
• Ownership: a lockable front door (owner, co-owners, friends), a secure chest that is not part of the town vault, furniture placed from the crafted catalog.
• Buildings take damage and can be broken like every static (#66); repair costs materials. What happens to a house when its plot is released or its town is plundered is decided here.
• Works with player-building-design, which keeps the full design (free building, claims outside towns, upkeep).

Done when a tester can hold a plot, deliver materials, see the house rise, lock it and store things in it, and another player can break into it.