Dataflake-docbuilder

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- Now using pkg_resources.parse_version to parse the tag names and
produce correct release ordering for each package
- Instead of using a flag to set the revision control system
across all packages you now specify the revision control system
per package with a simple prefix::

[hg]http://myserver/hg/mypackage
[svn]https://myservr/svnmypackage

For backwards compatibility, all URLs without prefix are assumed
to point to a Subversion repository.

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- Feature: You can now use either ``Subversion`` or ``Mercurial``
to check out documented packages.

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- Feature: If no standard package documentation can be found,
the setuptools ``long_description`` settings is used as a
last fallback to at least generate a single page for a package.

- Feature: To style the ``long_description`` fallback ReST
documentation, a new parameter ``fallback-css`` can be used to
provide a path to a CSS file.

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- Bug: If the ``z3csphinx-output-directory`` was set, all its
contained packages ended up on the index document. Now this
only happens if no SVN source URLs are otherwise provided.
If they are, only packages from those source URLs are
considered for linking on the index document.

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- Feature: If you generate some documentation via
`z3c.recipe.sphinxdoc` and want to stitch links to it
into the generated index file, you can use the new
``z3csphinx-output-directory`` parameter to point the script
to the generated package documentation root folder.

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- Bug: Don't clean up intermediate files, otherwise it is not
possible to re-use a template folder for creating several
separate pages into an output folder.

- Bug: Clean up group header creation to avoid header level
mixups.

- Bug: When creating a missing required index.rst, use a
template file if it exists.