2.0 Feature Documentation

[DanielRosenwasser]

As per @mhegazy's email:

• null (Add documentation for null/undefined/never and strictnullchecks #313)
• undefined (Add documentation for null/undefined/never and strictnullchecks #313)
• never (Add documentation for null/undefined/never and strictnullchecks #313)
• strictNullChecks section (Add documentation for null/undefined/never and strictnullchecks #313)
• UMD (Add documentation for UMD pattern #309)
• readonly properties and index signatures (Add documentation readonly properties and index signatures #311)
• this in functions (Add documentation for this in functions #310)
• Shorthand ambient module declarations and wildcard matching in module names (Add documentation for Shorthand ambient module declarations and wildcard matching in module names #308)
• new compiler options
• --lib (Document --lib flag #291)
• Discriminated union types (Add documentation for Discriminated union types #312)
• glob support (Add documentation for include and exclude with glob support #324)
• --noUnusedVariables and --noUnusedParameters
• /// <reference types=".." /> documentation (Add documentation for /// <reference types=".." />  #348)
• Refresh the playground