WIP - Package and Mirror history tracking

Still work in progress.
Add tracking of packages on apt repo servers/mirrors.
- Store every package version present on the mirror at time of check
- Compare tracked packages with mirror to find outdated versions

Signed-off-by: Christoph Kassen <c.kassen@telekom.de>
WIP - API work for outdated packages

Pushing this upstream so we can rebase other branches on top of it
and continue to work in it in parallel.

Changes include:
- updates to the module import handling
- bugfixes to make the packages list api returning data again
- unit test updates
- a simple command to prepopulate the database for testing purposes

Signed-off-by: Christoph Kassen <c.kassen@telekom.de>