minor local variable rename
minor local variable rename, and add child group
refactory debug print out
rename local variable
trigger "duringDel" event  in del , because model is deleted, the subscription is also deleted, and subscription of "afterDel" can not be triggered.
 So add "duringDel" to give a chance to respond. a toggle method
update readme
rename *skipSet to *fakeSet, *skipGet to *fakeGet, and some local variable rename
update download files