Branching an experimental version of puavo-sharedir-manager.
This uses paths by puavoId, so that school and group names
and displaynames may be changed without problems (files are
associated with group identity, not group names).
Also should make language support transparent:
people with different languages may share the same
files, and yet see the paths in their own language.

Nevertheless, this is a work in progress, and currently
looks like a real mess.
Now we have PuavoShareSpec-class, and directory definitions
look nicer now, but of course this is still broken.
Fix a few bugs.
Now directory and link structures are mostly okay,
and this should work.  (Some details are still unresolved, though).
Now things look okay, but I need to test/audit this stuff.
Force symlinks to new destinations if those already exist.
More securely forcing the symbolic links to point to
the right targets (no dereferencing, and make sure
only files under /home/share can be removed).
Now the ACLs finally look correct, because only the leaf
directories are set as shares.
dir_type is basically useless, so just remove it.
Remove unused modules and add some documentation.