[explorev2] adding support for client side validators on controls (#1920)

* Adding support for client side validators on controls

* Applying validators to more fields

* Addressing comments

superset/assets/javascripts/explorev2/components/ControlHeader.jsx

@@ -0,0 +1,48 @@
+import React, { PropTypes } from 'react';
+import { ControlLabel, OverlayTrigger, Tooltip } from 'react-bootstrap';
+import InfoTooltipWithTrigger from '../../components/InfoTooltipWithTrigger';
+
+const propTypes = {
+  label: PropTypes.string.isRequired,
+  description: PropTypes.string,
+  validationErrors: PropTypes.array,
+};
+
+const defaultProps = {
+  description: null,
+  validationErrors: [],
+};
+
+export default function ControlHeader({ label, description, validationErrors }) {
+  const hasError = (validationErrors.length > 0);
+  return (
+    <ControlLabel>
+      {hasError ?
+        <strong className="text-danger">{label}</strong> :
+        <span>{label}</span>
+      }
+      {' '}
+      {(validationErrors.length > 0) &&
+        <span>
+          <OverlayTrigger
+            placement="right"
+            overlay={
+              <Tooltip id={'error-tooltip'}>
+                {validationErrors.join(' ')}
+              </Tooltip>
+            }
+          >
+            <i className="fa fa-exclamation-circle text-danger" />
+          </OverlayTrigger>
+          {' '}
+        </span>
+      }
+      {description &&
+        <InfoTooltipWithTrigger label={label} tooltip={description} />
+      }
+    </ControlLabel>
+  );
+}
+
+ControlHeader.propTypes = propTypes;
+ControlHeader.defaultProps = defaultProps;