Added :scale parameter.
Added pucks.worlds.dev.world12 to demo :scale.

This is the same as pucks.worlds.dev.world6 aside from the reduced
scale and larger screen size.
Improved neighbor-finding algorithm to scale better.

Eddie Pantridge provided a draft implementation, which was revised by
Lee Spector to produce the version in this commit.
Created full, busy, multi-threaded pucks.worlds.dev.world13.

Also fixed click-to-inspect to work properly in scaled worlds.
Developed spawning physics, spawners, and dev.world14.
Tweaks to readme regarding spawning.
Added nursery-threshold parameter.

If there are this many or more active pucks in the world then nurseries
will not generate new pucks.
Allow nurseries to give inventory/memory + ai.world7.
Version bump.
Color property change proposals implemented.

Also began work on swarmevolvers and a related demo world.
Allow :eye-color and :core-color properties proposals.
Several changes/fixes + swarmevolvers.

Added :nursery-threshold setting: the number of active pucks below
which nurseries may generate new pucks.
Widened ventbox gates in ai.world6 and ai.world7.
Vents no longer give energy to torpedoes.
Added :torpedo-energy setting.
Added rotational-difference and limit1 utility functions.
Spawned pucks retain :genome entry of :memory specified by spawning
parent.
Created swarmevolver agents and dev.world15 to demonstrate them.
Updated README in several small ways.
Version bump.
Don't update steps in stones.
Fixed ventboxes again in ai.world6 and ai.world7.
Added ai.world8 which includes map donors.

+: removed unused functions in ai.world7 and ai.world7
+: commented out printing to terminal on click
Added file for mapdonors, dev.world16, changed ai.world8.

Reworked maps as memory rather than inventory items.
The dev.world16 namespace demonstrates the use of a map. The ai.world8
namespace is a challenge to develop user agents that can survive in a
world with ventboxes, key donors, and map donors.
Added puck :thrust-angle.
Fixed off-by-1 bug in neighbors.clj.

It was previously making the grid too large, with the consequence that
sensing around the edge of the world was not working correctly.
Added pucks.worlds.dev.world17 to demo :thrust-angle.
Note contributors in README.