added qstep as a variables for Calc2D.
added qstep as a variables for Calc2D.

lewisodriscoll/sasview,SasView/sasview,lewisodriscoll/sasview,SasView/sasview,lewisodriscoll/sasview,lewisodriscoll/sasview,SasView/sasview,SasView/sasview,lewisodriscoll/sasview,SasView/sasview,SasView/sasview