fix ie8 scrollbar issue
bug fixed: the icon inside groupbox should show well when groupbox open
borderlayout style minor fix
style fixed: the close icon of errorbox should show well when it open in
ie8
style fixed: the button of header and itself should not use filter
notification style fixed: the icon should show well when no reference
fine tune less variables
Merge branch '7.0' of https://github.com/zkoss/zk into fix-ie8

Conflicts:
	zul/src/archive/web/js/zul/grid/less/grid.less
	zul/src/archive/web/js/zul/sel/less/listbox.less
	zul/src/archive/web/js/zul/sel/less/tree.less
reset Z65-Flex-025.zul
bug fixed: the checkbox of selectwidget should look good when it checked
bug fixed: the faker-bar of checkmark tree should exist in ie8