The accordion widget was previously being passed true and false, where as it either expects true or the integer of the panel to show.
This fix sets it as either false or 0.
* Use jquery ui accordion for the field, and implemented an admin theme.
* Made the setting of configuration consistent with other form fields.
* ToggleComposteField->startClosed() has been deprecated in favour of
setStartClosed().
* Removed public access to the heading level, instead use getHeadingLevel()
or setHeadingLevel().
API CHANGE Removed several unsed JavaScript globals: sprintf(), Number.prototype.CURRENCIES, Number.prototype.toCurrency(), String.prototype.ucfirst(), jQuery.fn.clearFields(), jQuery.fn.clearInputs()
MINOR Removed prototype_improvements.js and jquery_improvements.js files, now contained in individual component code (or removed altogether)
