fix(datepicker): allow expressions for minMode/maxMode

- Fixes expressions not being parsed for `min-mode` and `max-mode`

Closes #5264
Closes #5268
Fixes #5240

Author: luber

Diff for: src/datepicker/datepicker.js

@@ -656,16 +656,7 @@ function(scope, element, attrs, $compile, $parse, $document, $rootScope, $positi
       });
     }
 
-    angular.forEach(['minMode', 'maxMode'], function(key) {
-      if (attrs[key]) {
-        scope.$parent.$watch(function() { return attrs[key]; }, function(value) {
-          scope.watchData[key] = value;
-        });
-        datepickerEl.attr(cameltoDash(key), 'watchData.' + key);
-      }
-    });
-
-    angular.forEach(['datepickerMode', 'shortcutPropagation'], function(key) {
+    angular.forEach(['minMode', 'maxMode', 'datepickerMode', 'shortcutPropagation'], function(key) {
       if (attrs[key]) {
         var getAttribute = $parse(attrs[key]);
         var propConfig = {