Fix bare handler variable name in SHtml.handler.
Put form handlers in SHtml.handler in form group 1
Fix return value for attribute SHtml.handler.

Before we were appending the attribute, but attribute
bindings are guaranteed to be setting an attribute, so we
instead return the value for the attribute.
Fix submitAjaxForm in SHtml.ajaxHandler binding.
Add proper mapHandlerFunc and makeAjaxCall logic.
Finish ajaxHandler first-pass implementations.

Still FIXMEs sprinkled throughout and no API docs.