ZF-12146: No way to clear _messages array
Zend_Form_Element supports clearing Decorators, Filters, ErrorMessages, and Validators. It does not, however, support clearing Messages. To make it so that no error message is displayed for an invalid field, Validators, ErrorMessages, and Messages all need to be cleared.
I'd like support for Zend_Form_Element::clearMessages() that simply resets the $this->_messages array to empty.