changed width and height to robot-range-x and robot-range-y and made
them constants

because technically, the robot ranges are the maximum ranges for the
centers of the robots' bodies,
so the actual extent of the arena when
displayed must be slightly larger
moved test-programs out of test into src, renamed it src-programs

also fixed some testing bugs that were using
the old parameters for init-world
each new index.html request now initiates a new game instance
added Geom module for geometric calculations
updated comment for worlds constructor
altered :moving-to-spot program so it sets the gun aim to a random direction
refactored scaleFactorX & Y stuff into functions, in main.js
changed name of draw function to drawWorld, main.js
refactored drawing of circles; added drawing of lines, and guns
refactored 'register' with path-to-robot-field convenience function
altered indentatin in register
moved single-use read- and write-register functions directly into the extend protocol blocks as anonymous functions
refactored register to be able to use mixins separate from their
map keys
added SHOT register and :shot-timer robot field.

:shot-timer does not count down yet, and SHOT register
does not release shells.