improve bit-manipulation concept

[mikedamay]

Currently, bit-manipulation concept is focused on flag-enums. The concept should be rewritten to introduce the student to bits, bitwise operations and anything else that would typically occur in an introductory text on the subject.

Assume that numbers and compound assignment operators, +=, *= etc, are prerequisites (and have been explained elsewhere).

Obviously, much of the material can be links to external documentation and arguably this document.

Note that this document will need to be updated with the new link to C#'s bit-manipulation but the landscape may have changed depending on what happens to introductions. It is a moving target but if it's not straightforward to change the link then just raise an issue and our leader will give us direction.