Merge pull request #641 from jeff1evesque/python_data_validator

#640: data_validator.py, adjust allowable MIME types
#642: html_form.js, ajust acceptable MIME type html message
Merge pull request #643 from jeff1evesque/js_html_form

#642: adjust acceptable MIME type html message
#645: form_validator.js, add 'application/xml' mime type
Merge pull request #646 from jeff1evesque/js_form_validator

#645: form_validator.js, add 'application/xml' mime type
#644: data_validator.py, add 'text/plain' as valid option in acceptabl_type