- Removed advanced (import/export) view - superfluous.

- new() and new_or_existing() methods now accept a wrap_with argument.
  If wrap_with is non-None, the data object returned will be wrapped
  in (via __of__) with the object passed into the wrap_with argument.
  This will facilitate the wrapping of data objects in the calling
  session data manager object.

- Transient objects no longer keep a reference to their container.
  Instead, containers use the isValid method of objects to determine
  whether an object is valid.  An object no longer deletes itself from
  its container and relies solely on this mechanism.

- Callback handling now logs on failure.

- Various deletions of commented material.

- getToken of data objects returns the key with which they were entered
  into their container, while getId returns a uniform unique id.  getName
  is now aliased to getId.

- data objects now no longer aq-unwrap things stored in them.  This
  is a security change.

- repr method of data object now returns simpler structure.

- removed stx workarounds from interfaces file (we should just fix the
  help system instead of doing stuff like  _, etc.)

- extended some descriptions of interfaces.

- extended and edited other docs.

TODO:

- fix tests to run under testrunner.

- "ring" must change to become more conflict resistant.
  (new data structure and algorithm needs to be put in)

-  need new icon for data container.

- need out of memory protection in container.

misshandles URLs containing semicolons (path-segment parameters.

None.  If a non-resolvable conflict error occurs, we try to coerce
serial to something more humanly readable, but U64() can't be passed a
None, so let's be a bit more robust.

the environment.  No type checking is done, except that if env is not
a string or not None, then it's the caller's responsibility to pass in
a valid DBEnv.

that a pickle could contain references to objects we don't know
about (i.e. that isn't in our _serials table).  I'm not completely
sure why this could happen, but this makes pack() a little more robust
in the face of such anomolies.

This broke at least WebDAVs MOVE and COPY operations.

1.0 release.  These changes pass all the tests, but the proof will be
packing some real data (to come next -- this stuff has to be checked
in first).  Specifically,

__init__(): We now allocate a pack-lock which is acquired in pack() to
prevent multiple threads from packing at the same time.  This should
be deadlock-proof because you should never have the storage lock when
you want to acquire the pack lock (but I could be missing something
obvious).

_rootreachable(): New method which calculates the set of object ids
reachable from the current revision of the root object.

_zapobject(): Rewritten to remove the recursion.  It populates a
dictionary (passed in the parameter) with the oids for any objects
whose refcounts went to zero because of the object we're now zapping.

_zaprevision(): Same deal as _zapobjects().

_dopack(): The guts of the pack() operation, done this way so pack()
itself can just be a wrapper around _dopack() with pack lock
acquisition/release.  This also does not acquire the storage lock
until it actually has to start zapping revisions, and it releases and
reacquires the lock for each revision it zaps.  This gives other
threads an opportunity to do work during a pack, which should never
impact the pack as any work they do will happen in the future (and
we're safe against bogus future pack times).

pack(): Acquire the pack lock, _dopack(), release the pack lock.

Also, move the opening of the output and log files above the opening
of the storages so there's a closer link between that and the
try/finally that closes closes the storages.