Overload the Convert function to allow a input UoM and output UoM for unitless values

For unitless values you can assign a unit of measure by using the Convert() function. To further convert this to another UoM in the same class you need to nest another Convert() function.

For example, Convert(Convert(3600, "s"), "h"))

It would simplify expressions if this conversion could be achieved in one step making expressions much easier to read/debug.

For example, Convert(3600, "s", "h")