Interface changes

Behavior changes that may affect your projects

• If two instances of a MemoryFile point to the same file, renaming one no longer makes the second one point to the new filename. AbstractFile and AbstractFolder instances should always be "tied" to their filename.

Other minor changes and bug fixes

• MemoryFile and MemoryFolder are now strongly bound to their filename. Renaming a MemoryFile while another one points to the same name does not rename the second instance.