delegating to the base storage.

Added a cleanup method that delegates to the base storage.

- Changed the signature for registerDB to ommit the unused second
  argument.  DB, the normal caller of registerDB will work with the
  old signature.

- Loosened the input requirements to invalidate to not require a
  dictionary with unused keys.

- Added a references function to give storages a way to extract object
  references from database records that will work with storage
  adapters that might change the record format, for example through
  encryption or compression.

can cause signidficant delays, especially on systems with very
course-grained sleeps, like most linux systems.  This change makes the
ZEO tests run about 25% faster on an Ubuntu desktop system.  We
suspect the production impact to be much greater, at least on some
systems.

Removed some non-async code, now that we no-longer have a non-async
mode. (I cowardly left an assert behind to make sure.:)

   on others.

  improved in the case that servers are restarted.  Before, if
  transactions were committed after the restart, clients that were up
  to date or nearly up to date at the time of the restart and then
  connected had to verify their caches.  Now, it is far more likely
  that a client that reconnects soon after a server restart won't have
  to verify its cache.

- Fixed a serious bug that could cause clients that disconnect from and
  reconnect to a server to get bad invalidation data if the server
  serves multiple storages with active writes.

invalidation queue.

 - added test for custom openDetached() class

 - added notice to history txt that zodb 3.8 now contains blobs :)

These files were missing:

  BTrees/Development.txt
  ZEO/scripts/README.txt
  ZODB/scripts/README.txt
  ZODB/scripts/referrers.txt

 - moved setuptools import in setup.py before distutils import to allow
   setuptools to apply its patches

add missing file and fix setup.py so the error would have been caught when I ran the tests before the previous checkin

  all be accessed with those names in the modules (e.g.,
  BTrees.IOBTree.BTree).  This is in addition to the older names (e.g.,
  BTrees.IOBTree.IOBTree).  This allows easier drop-in replacement, which can
  especially be simplify code for packages that want to support both 32-bit and
  64-bit BTrees.

- Describe the interfaces for each module and actually declare the interfaces
  for each.

- Fix module references so klass.__module__ points to the Python wrapper
  module, not the C extension.

(For now, we're retaining compile-time support for making the
   regular integer BTrees 64-bit.)

the main method call needs to be lowercase, otherwise the call will raise a TypeError: Main() takes no arguments (2 given)

It isn't actually a script but it is used in the same spirit.  Maybe
it will be a script someday.

(Merged from 3.7 branch.)