[kronolith] Migrating Kronolith data to new instance

[r.wiesbach at web.de]

I noticed that our Kronolith server does no longer send invitation
emails when adding users to an appointment. As a first step of debugging
I intended to upgrade to the current version (apt upgrade, pear upgrade
and pecl upgrade) and I noticed there are a lot of dependencies that
seem to be nontrivial to migrate from php5 to php7. Avoiding the
dependency hell I would like to have a fresh ubuntu LTS with horde
Kronolith. However I cannot find a documentation about how to extract
data (users account, calenders, tasks and if possible configuration as
well). Yes, I can clone the sql database, but that would be kind of
dirty again wouln't it?