This is reverting templates back to pre-3.0 conventions,
which were dominated by XHTML templates.
HTML5 allows both self-closing and unclosed tags,
so opting for self-closing to achieve maximum compatibility.
BUGFIX Remove legacy code and template which is never picked-up so that TextareaField becomes 'readonly' when it is transfered to readonly field. Change TextareaFieldTest test cases to address a 'readonly' textarea field displaying the special html characters correctly.