Tree Mode

new ActionType: ActionType.UpdateTreeGroupsExpanded
actionCreator: updateTreeGroupsExpanded(rowKeyValue: any)

new props:

  treeGroupKeyField?: string; 
  treeGroupsExpanded?: any[]; // undefined - all rows are expanded

Demo: https://komarovalexander.github.io/ka-table/#/tree-mode
Docs: http://ka-table.com/docs_props.html