MDL-59382 theme: bring the date picker forward

theme/bootstrapbase/less/bootstrap/variables.less

@@ -147,7 +147,7 @@
 @zindexFixedNavbar:       1030;
 @zindexModalBackdrop:     1040;
 @zindexModal:             1050;
-
+@zindexModalContainer:    4050;
 
 // Sprite icons path
 // -------------------------

theme/bootstrapbase/less/moodle/calendar.less

@@ -22,6 +22,9 @@
 
 // Calendar restyling.
 .path-calendar {
+    #dateselector-calendar-panel {
+        z-index: @zindexModalContainer+4;
+    }
     .calendartable {
         width: 100%;
         th,

theme/bootstrapbase/less/moodle/modal.less

@@ -10,7 +10,7 @@ body {
     right: 0;
     bottom: 0;
     left: 0;
-    z-index: 4050;
+    z-index: @zindexModalContainer;
     outline: 0;
     overflow-x: hidden;
     overflow-y: auto;

theme/bootstrapbase/style/moodle.css

@@ -5551,6 +5551,9 @@ img.iconsmall {
 .calendar_event_user {
   background-color: #dce7ec;
 }
+.path-calendar #dateselector-calendar-panel {
+  z-index: 4054;
+}
 .path-calendar .calendartable {
   width: 100%;
 }