L3 - Default Date picker of the generated task forms doesn't work as expected on version 7.11 and above as
angular directives for bootstrap has been updated from version 0.11.2 to 2.5.0 where uib-datepicker-popup attribute should be used instead of datepicker-popup
Which means HtmlFormEngine class should be updated such as this line of code
protected static final String DATEPICKER_POPUP_ATTRIBUTE = "datepicker-popup";
should be replaced with below one
protected static final String DATEPICKER_POPUP_ATTRIBUTE = "uib-datepicker-popup";