Puts back upload help for docker
Adds pack format history

Currently, these match the software version.
Splits pack format version from software version

Reprozip and ReproUnzip 0.5 use the exact same format as 0.4.

Let's stop using the same number for both, and roll back to 0.4.
Better message for unknown config version
Merge branch 'pack-format-version' into 'master'