[WIP] Add immutable number

[rande]

No description provided.

[rande]

The immutable object is usefull if you want to display a price without changing the object itself.

$product->getUnitPrice()->mul($quantity = 4) ...

[rande]

@ramsey Any comment on this PR ? I will add unit test on the class if you are agree on the change. By the way the changes are BC

[ramsey]

I had to take time to review the changes, and it looked like there were a lot of them, but that's just because of all the whitespace changes.

Everything looks good. Please add the unit test, and I'll merge in the changes.

Thanks for contributing this!

[rande]

Thanks for the feedback, I will do the unit test ASAP.

Thanks

[stefanotorresi]

@rande any update on this? I'd very much like this functionality. If you don't have the time let me know, I could pick this up.