A bajillion detached heads whaaat's going on.
Tidy/Refactor

Largely housekeeping. A smidge of optimization and now sizes the field
to the window if you reset.
More refactoring

Separated update into calculating forces and integrating.
velocity Verlet integrator
renamed velVerlet to leapfrog and added true velVerlet
more tidying, put profiler back

Graphics are now showing up as a thing that takes time.
Collision detection but no merging
forgot one thing
Paramatised some values
Divorced framerate from dt from numsteps

Also let Body take care of its own radius, color, and mass calculations.
Merged back in to Master