Adding or adjusting front-end function and variable documentation per our conventions.

Adding or adjusting front-end function and variable documentation per our conventions.
* Adding "return this;" in object constructor functions.
* Added test suites for Map and Message object constructors to match the @return descriptions.

Also did some trivial clean up and performance optimizations while at it. (per http://www.mediawiki.org/wiki/JavaScript_performance )

/me has been infected by Reedy and will be doing more of this tonight.