added the sharing of new collaborators, with other collaborators.
changed the way the visibility flag is set
changed check of connection disposal
added error handling of attempting to attach a file from a project that has no collaboration attached.
code clean up, warnings removed.
adjusted errorhandling
renamed FileChangeManager to FileChangeListener
renamed FileChangeManager to FileChangeListener
moved calculation of hash away from tree structure
code clean up
added messaging/error notification between collaborators