Add box-shadow to Mail editor

UI/WebServerResources/scss/views/MessageEditorUI.scss

@@ -9,7 +9,11 @@
   width: (13 * $pitch + $mg); // 13 cols + 1margin for scrollbar
   margin: 0 auto;
   overflow: auto;
+  height: 100%;
   background-color: sg-color($sogoPaper, 100);
+  transform: translateY(-1 * $pitch);
+  z-index: 40;
+  box-shadow: $whiteframe-shadow-z1;
 }
 .buttonsToolbar {
   padding: $mg 0;