For MountPoints, symbolic links etc to work, then folders can not have pointers
to their parents, since the concept ot parent is no longer well defined.

How should events proagate in trees?
  We do not want events from folders which we don't care about
     When adding or removing from a folder, should check the caredFor flag
     The caredFor flag is initially false
       It is set to true when someone calls ICare(true) on the folder.
       A folder which was not cared about but for which someone now cares should
         fire notify events for all its children

  MountPoints must propagate events from the mounted tree to the parent tree.
    To do this they must listen to their own tree, and modify the event by 
       replacing original prefix with a new prefix.
     
  