Added numbers class

[mariabernis]

⚠️ Includes code from previous #2 pull-request

This pull/request starts at 9244c5f commit from #2.

🎩 What? Why?

Added GZNumbers class to generate random numbers. It allows:

• Creating random bools and random bools with a predominant value.
• Creating random integers and random integers with a predominant or scarce value.
• Obtaining random indexes from a collection or string.
• Creating random float numbers.

All API is tested using Expecta (added in previous pull-request).