This involves a deep upgrade. Changing base distribution from debian
towards alpine, and changing the way the schedule-command relation is
handled. Consequences:
- size of image went from 195MB to 45MB
- build process simplified (only one small ``Dockerfile``)
- dependencies are not in the charm anymore but fetched on build
from our download server
- local cron business intelligence was moved in the cron charm
- extreme simplification for implementing run-once charms relation with
cron.
- some simplification for charms that adds some intelligence on their
side.
Includes ``mirror-dir-check`` with the ``mirror-dir check`` call, the
replacement of ``mirror-dir`` call is ``mirror-dir backup``. An additional
``mirror-dir report`` was added.
Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>