pySCG: Numbers related landing page to explain generic issues

[myteron]

Numbers landing page to explain generic issues around:

• Hardware limitations
• A Python int can be much bigger than what is known as 64 bit int and why NUM13 does not apply
• Python relation to primitive int numpy ctypes
• implicit conversion can come unexpected
• explicit conversion can have unexpected results.
• Upper boundaries
• Lower boundaries.

Content that is helpful for understanding numbers or above points and applicable for all numeric related issues such as
Avoid loss of precision when converting primitive integers to floating-point