Whitespace in denial constraints leads to DCFormatException

[pmaetzig]

When specifying a denial constraint, adding whitespace after the comma like so

t1.EQ(t1.petal_width, t1.sepal_width)

leads to this error

DCFormatException: Tuple name t1 not defined in EQ(t1.petal_width, t1.sepal_width)

and the DC not being read. I suppose no whitespace must be used in DCs, it would be helpful to include this fact in the tutorial (and/or a comment).

Benefit: making sure users comply with DC formatting Cost: adding one sentence to the tutorial