Grey the SQL panel in edit data mode. Fixes #1423

Introduced a new class 'cm_disabled' with css property background-color to '#EEEEE'
Query tool in edit mode, add the class 'cm_disabled' to set background color to dark and set the cursor property to 'nocursor' to disable editor.
Increased the query tool title padding to fix the issue of whitespace below the title.

web/pgadmin/static/css/overrides.css

@@ -1359,3 +1359,8 @@ table.backgrid {
 .aciTree.aciTreeLoad {
   background: none;
 }
+
+/* class to disable Codemirror editor */
+.cm_disabled {
+  background: #EEEEEE;
+}

web/pgadmin/tools/sqleditor/static/css/sqleditor.css

@@ -35,7 +35,7 @@
 
 .editor-title {
   background-color: #2C76B4;
-  padding: 2px;
+  padding: 4px 5px;
   color: white;
   font-size: 13px;
 }

web/pgadmin/tools/sqleditor/templates/sqleditor/js/sqleditor.js

@@ -1124,7 +1124,12 @@ define(
             }
           }
           else {
-            self.gridView.query_tool_obj.setOption("readOnly",true);
+            // Disable codemirror by setting cursor to nocursor and background to dark.
+            self.gridView.query_tool_obj.setOption("readOnly", 'nocursor');
+            var cm = self.gridView.query_tool_obj.getWrapperElement();
+            if (cm) {
+              cm.className += ' cm_disabled';
+            }
             self.disable_tool_buttons(true);
             self._execute_data_query();
           }