The versioning information doesn't sit very well in the releasing
packages guide. Add this to the information on binary package
versioning to make a more holistic page on versioning.

Move the information on dch tags to the version_control guide where
it is mentioned.

The rest of this guide is very out of date. We have a number of other
guides on releasing packages, drop this one.

Signed-off-by: Martyn Welch <martyn.welch@collabora.com>