Consider eliminating commands that don't move the pen

[rsheeter]

Ref discussion and example at #279 (comment). Problem is not limited to arcs, any command with no pen movement seems potentially cullable.

Note that the change to >= 0 in #279 might want to go back to > 0 if we add such a cull.

[rsheeter]

Thinking "aloud," if we ever add variable support we'd need to generalize to only cull if the command has no pen movement in all instances of the glyph.