vpath file - add a keey property to know if obj should be kept around

vpath file - add a keey property to know if obj should be kept around

if its a file downloading (to a tmp location) or a zip/tar/whatever
file being extracted also to a tmp location and that tmp file needs to
be removed after ...you need to keep the obj around to know when to
delete the file. this makes the keeping optional and you query if the
vpath obj is meant to be kept or not. if it's not it's safe to del
immediately.

this cuts down 1 obj per image obj/edje obj when generally unused.
save some mem.