Add bit_count function

[joente]

Description

This pull request add's a function bit_count() for integer type and returns with the number of bits turned on in the integer value.

Usage:

(42).bit_count();  // returns 3 (binary: 0b101010)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Update collection functions test

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• New and existing unit tests pass locally with my changes