[sql-lab] fix react warnings in dev (#1232)

* rename file to match class

* fix react warnings

* fix proptype typo

* add missing keys

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

@@ -64,7 +64,7 @@ class TableElement extends React.Component {
       metadata = (
         <div>
           {this.props.table.columns.map((col) => (
-            <div className="clearfix">
+            <div className="clearfix" key={shortid.generate()}>
               <div className="pull-left m-l-10">
                 {col.name}
               </div>