Release - v5.0.3

Release Notes

I've added the command factorial. fact can also be used. This allows for the top of the stack item (line1) to to exectute as a factorial.

Example:
4! = 1x2x3x4 = 24

The number used must be greater than zero and only integers will be processed. So if you do have a decimal portion, it will be dropped (not rounded) before the factorial calculation.

I've v5.0.2 added scientific unit tests everywhere it should matter so I can be fairly confident as changes are made the results will be accurate.