RFE: apkg test

Implement a packaging testing command apkg test based on Debian autopkgtest.

apkg test should:

• install testing requirements
• run all tests
• present test result in a nice readable format

A mechanism to define and select proper test requirements is needed. In autopkgtests this is done through debian/tests/control file, but that's distro-specific, we need to efficiently define requirements for all supported distros.