[IMP] web: datetime picker style

Changed the style of the "Close" button to match the one on the "primary buttons".

Task 2068164

addons/web/static/src/js/widgets/date_picker.js

@@ -42,7 +42,7 @@ var DateWidget = Widget.extend({
                 next: 'fa fa-chevron-right',
                 today: 'fa fa-calendar-check-o',
                 clear: 'fa fa-delete',
-                close: 'fa fa-times'
+                close: 'fa fa-check primary',
             },
             calendarWeeks: true,
             buttons: {

addons/web/static/src/scss/datepicker.scss

@@ -84,6 +84,20 @@ div.dropdown-menu.bootstrap-datetimepicker-widget{
     }
 }
 
+.picker-switch {
+    span.fa {
+        margin: 0;
+        @include transition($btn-transition);
+        &.primary {
+            background-color: $o-brand-primary;
+            color: white;
+            &:hover {
+                background-color: darken($o-brand-primary, 10%);
+            }
+        }
+    }
+}
+
 // This is rtl language specific fix
 // it will fix the user agent stylesheet padding
 // and transform the prev and next icons