Misc code cleanup.
Working AJAX form replacement function for landing page.
Minor code cleanup, commenting added.
Incomplete version using AJAX.
Non-AJAX, DHTML-only approach;
AJAX wasn't necessary, since possible content for form is limited to two known options;
DHTML may avoid issues with variables populated by PHP, and other quirks of loading elements piecemeal;
Merge remote-tracking branch 'remotes/github/landingPageTweaks1b'