[sqllab] add support for results backends (#1377)

* [sqllab] add support for results backends

Long running SQL queries (beyond the scope of a web request) can now use
a k/v store to hold their result sets.

* Addressing comments, fixed js tests

* Fixing mysql has gone away

* Adressing more comments

* Touchups

caravel/assets/javascripts/SqlLab/components/App.jsx

@@ -5,6 +5,7 @@ import TabbedSqlEditors from './TabbedSqlEditors';
 import QueryAutoRefresh from './QueryAutoRefresh';
 import QuerySearch from './QuerySearch';
 import Alerts from './Alerts';
+import DataPreviewModal from './DataPreviewModal';
 
 import { bindActionCreators } from 'redux';
 import { connect } from 'react-redux';
@@ -26,8 +27,9 @@ class App extends React.Component {
     this.setState({ hash: window.location.hash });
   }
   render() {
+    let content;
     if (this.state.hash) {
-      return (
+      content = (
         <div className="container-fluid">
           <div className="row">
             <div className="col-md-12">
@@ -37,16 +39,18 @@ class App extends React.Component {
         </div>
       );
     }
+    content = (
+      <div>
+        <QueryAutoRefresh />
+        <TabbedSqlEditors />
+      </div>
+    );
     return (
       <div className="App SqlLab">
+        <Alerts alerts={this.props.alerts} />
+        <DataPreviewModal />
         <div className="container-fluid">
-          <QueryAutoRefresh />
-          <Alerts alerts={this.props.alerts} />
-          <div className="row">
-            <div className="col-md-12">
-              <TabbedSqlEditors />
-            </div>
-          </div>
+          {content}
         </div>
       </div>
     );