message: [sql lab] Update event handler name
  Update SqlEditor database change event handler name to be more specific.
diff: @@ -35,7 +35,7 @@ class SqlEditorLeftBar extends React.PureComponent {
  this.fetchSchemas(this.props.queryEditor.dbId);
  this.fetchTables(this.props.queryEditor.dbId, this.props.queryEditor.schema);
  }
  - onChange(db) {
  + onDatabaseChange(db) {
  const val = db ? db.value : null;
  this.setState({ schemaOptions: [] });
  this.props.actions.queryEditorSetSchema(this.props.queryEditor, null);
  @@ -144,7 +144,7 @@ class SqlEditorLeftBar extends React.PureComponent {
  '_oc_DatabaseView=database_name&' +
  '_od_DatabaseView=asc'
  }
  - onChange={this.onChange.bind(this)}
  + onChange={this.onDatabaseChange.bind(this)}
  value={this.props.queryEditor.dbId}
  databaseId={this.props.queryEditor.dbId}
  actions={this.props.actions}
  