[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/HighlightedSql.jsx

@@ -0,0 +1,44 @@
+import React from 'react';
+import SyntaxHighlighter from 'react-syntax-highlighter';
+import { github } from 'react-syntax-highlighter/dist/styles';
+
+const HighlightedSql = (props) => {
+  const sql = props.sql || '';
+  let lines = sql.split('\n');
+  if (lines.length >= props.maxLines) {
+    lines = lines.slice(0, props.maxLines);
+    lines.push('{...}');
+  }
+  let shownSql = sql;
+  if (props.shrink) {
+    shownSql = lines.map((line) => {
+      if (line.length > props.maxWidth) {
+        return line.slice(0, props.maxWidth) + '{...}';
+      }
+      return line;
+    })
+    .join('\n');
+  }
+  return (
+    <div>
+      <SyntaxHighlighter language="sql" style={github}>
+        {shownSql}
+      </SyntaxHighlighter>
+    </div>
+  );
+};
+
+HighlightedSql.defaultProps = {
+  maxWidth: 60,
+  maxLines: 6,
+  shrink: false,
+};
+
+HighlightedSql.propTypes = {
+  sql: React.PropTypes.string,
+  maxWidth: React.PropTypes.number,
+  maxLines: React.PropTypes.number,
+  shrink: React.PropTypes.bool,
+};
+
+export default HighlightedSql;