Issue #498 - Fix blackout dates on movie datepicker (#512)

* Issue #498 - Update MovieManagerUI.js

Datepicker for advanced movie options blocks out dates that it shouldn't.

'maxDate' option defaults to null.
reference: https://flatpickr.js.org/options/

The option has been removed from flatpickr instance. This allows user to select future dates.

* #498 - Update MovieManagerUI.js

#512 PR review suggested further changes.

doOpen handler is entirely removed

resources/js/Media/MovieManagerUI.js

@@ -422,19 +422,11 @@ var MovieManagerUI = MediaManagerUI.extend(
 		//Movie Generation time pickers
 		$('#movie-start-date').flatpickr({
 			allowInput: true,
-			dateFormat: 'Y/m/d',
-			onOpen: function (selected, str, instance) {
-				var observationDate = new Date(Helioviewer.userSettings.get("state.date"));
-				instance.set('maxDate', observationDate.toUTCDateString());
-			}
+			dateFormat: 'Y/m/d'
 		});
 		$('#movie-end-date').flatpickr({
 			allowInput: true,
-			dateFormat: 'Y/m/d',
-			onOpen: function (selected, str, instance) {
-				var observationDate = new Date(Helioviewer.userSettings.get("state.date"));
-				instance.set('minDate', observationDate.toUTCDateString());
-			}
+			dateFormat: 'Y/m/d'
 		});
 		if ($('#movie-start-date').length > 0) {
 			$('#movie-start-date')[0]._flatpickr.setDate(new Date(Helioviewer.userSettings.get("state.date") - duration).toUTCDateString());
@@ -1157,4 +1149,4 @@ var MovieManagerUI = MediaManagerUI.extend(
 	}
 });
 
-export { MovieManagerUI }
+export { MovieManagerUI }