Page on Visibility Modifiers

[AndrewDiMola]

We really need a page that outlines all visibility modifiers and their consequences on scope.

Start with a page with sections on public, private, protected, and a table like https://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html that shows consequences on visibility.

Related:

• Expand the accessibility level of protected to super classes facebook/hhvm#9049
• Expand the accessibility level of protected to super classes facebook/hhvm#9049 (comment)