Proposed Enhancement: Extend the Rand function to allow seed, min and max

[bwakabats]

These are passed as optional parameters. So the Rand function has 4 versions:

• RAND()
• RAND(object seed)
• RAND(int min, int max)
• RAND(object seed, int min, int max)

I have also added Unit tests

[bwakabats]

This could now be implemented using the external function feature in #19