Rename 'Documentation' folder to 'Docs' for consistency

[asthana86]

There is a mix of lowercase and capitalization e.g. (Documentation vs. src, pkg, test) and usage of short vs. long names (e.g. Documentation vs. src, pkg, test).

Would propose renaming to the following:
Documentation -> docs

Thoughts?

[justinormont]

There is a related discussion for moving ZBaselines under the tests folder: #100

[asthana86]

Updated this to be specifically about docs.