ENH: Added optional limits to Function1 (#1924)

To apply limits to the input values, use the dictionary format to include the
optional keywords 'minLimit' and/or 'maxLimit', e.g.

    limitedPolyTest        polynomial;
    limitedPolyTestCoeffs
    {
        limitedPolyTest coeffs
        (
            (5 1)
            (-2 2)
            (-2 3)
            (1 4)
        );

        minLimit    0.4;
        maxLimit    1.4;
    }

    limitedTableFileTest   tableFile;
    limitedTableFileTestCoeffs
    {
        file            "<system>/fanCurve.txt";
        minLimit        0.4;
        maxLimit        1.4;
    }