Obtains a fully variable value range.

This factory obtains a range where both the minimum and maximum value may vary.

Parameters:

minSmallest		the smallest minimum value
minLargest		the largest minimum value
maxSmallest		the smallest maximum value
maxLargest		the largest maximum value

Returns:  the ValueRange for smallest min, largest min, smallest max, largest max, not null

Exceptions:

IllegalArgumentException

if the smallest minimum is greater than the smallest maximum, or the smallest maximum is greater than the largest maximum or the largest minimum is greater than the largest maximum