BRANCH SP-717:

  fixed some row color highlighting issues when selecting and deselecting multiple rows
  added TableGroupManageWdg for setting up advanced Grouping
  made grouping work with values containing non-ASCII words
  group_elements kwarg can be defined directly with ViewPanelWdg (e.g. category,status)
  modifed get_group_bottom_wdg for ExpressionElementWdg and SimpleTableElementWdg to return a tuple