Freitag-releaser

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- More verbose and more string formatting fixes.
[gforcada]

- Check that a distribution has a source defined on buildout before trying
to clone it.
[gforcada]

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- Be more verbose, so one know about which distribution the output is about.
[gforcada]

- Fix two strings that were not formatted.
[gforcada]

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- Add dry-run mode to fullrelease command.
[gforcada]

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- Add update distribution ``CHANGES.rst``.
[gforcada]

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- Add gather changelog command.
[gforcada]

----------------

- Cleanups and code reorganization.
[gforcada]

- Add full-release command.
[gforcada]