Fix Select2 issues. Fixes #1418. Fixes #1434

1. Select2 control fixed for multi-select mode.
2. Index constrains (primary and unique key) fixed column listing issue.
3. Table node "inherited from" (Select2 control) was not showing table name with public schema

web/pgadmin/static/js/backform.pgadmin.js

@@ -1790,7 +1790,11 @@
       return encodeURIComponent(rawData);
     },
     toRaw: function(formattedData, model) {
-      return decodeURIComponent(formattedData);
+      if (_.isArray(formattedData)) {
+        return _.map(formattedData, decodeURIComponent);
+      } else {
+        return decodeURIComponent(formattedData);
+      }
     }
   });