Non-deterministic dict iteration

[miklos1]

Running "python -R coughee.py" repeatedly gives slightly different results.

[miklos1]

More compact printing of the UFL form:

{ v_0 * w_5 * (w_3 + -1 * w_8) } * dx(<Mesh #-1>[everywhere], {})
  +  { v_0 * w_7 * (w_3 + -1 * w_8) } * ds(<Mesh #-1>[everywhere], {})
  +  { (((w_7)('+')) * ((w_3 + -1 * w_8)('+')) + ((w_7)('-')) * ((w_3 + -1 * w_8)('-'))) * 0.5 * (((v_0)('+')) + ((v_0)('-'))) } * dS(<Mesh #-1>[everywhere], {})