Tiddlyweb

* Add support for Python logging using the logging
module. See 'debug_level' in tiddlyweb/config.py.
* Request logging now goes to tiddlyweb.log instead
of stderr.

* Correct the handling of from_svn and instance plugins
when external plugins are used.
* No longer Set-Cookie with chkHttpReadOnly set to false,
ServerSideSavingPlugin now does this.
* No longer have a server failure when trying to use a sort
filter on an attribute that does not exist. Instead send
and HTTP 400.
* Add an "update" twanager command. See the help.

* Use the latest TiddlyWiki 2.4.2 beta.
* Update the docstore to use the latest client plugins and docs.
* Send server.workspace as a partial url fragment in wiki
serialization.
* Correct a minor error in twanager that could cause a warning.

* Increase the granularity of modified timestamps on
tiddlers, so Etag generation on lists of tiddlers
is based on seconds rather than minutes, avoiding
some (but not all) caching problems.

* Use sha instead of crypt for storing user passwords
so we are more compatible across multiple systems.
Unfortunately this is not backwards compatible with
existing created users.
* Update COOKBOOK to include some informationa about
http_proxy.

* Fix a typo in a plugin URL.