beta: Update from protocol 61 to 74.

Completely and totally untested, but hopefully enough to get people moving.

It's possible that the new 0xfe prevents clients from communicating with
Bravo. If that's the case, then we'll fix it, like we always do.
plugins/automatons: Allow grass to be deterministic in unit tests.
inventory: Clean up a couple algorithmic nits.

"I'm gonna make you a little less disgusting every day."
Fix up some pyflakes warnings.
ibravo, policy/windows: More work on IWindow.

Refs #409.
beta/protocol: Clean up b.p.windows-using code.

Refs #409.
bravo/world: Fix dictionary changing size during iteration.