Tests whether a 3D line geometry is digitised in an uphill direction.
An optional tolerance may be supplied to use when comparing the heights of vertices on the line. The line is considered to be uphill if each vertex is higher than all of the preceding vertices, to within the specified tolerance.
Parameter 1 - a 3D line geometry to be tested.
Parameter 2 (Optional) - a numerical value specifying the tolerance to apply to the line's z values.
Returns: a Boolean value, true if the geometry is a 3D line that slopes upwards and false otherwise. Returns null if parameter 1 is not a 3D simple line geometry.