Additionally add required "persistence" to test.

It is already requirement for slapos.core, and it is well known code.

Ue multiprocessing instead of threading, as there is no other way to kill
Flask application from code except SIGTERMing it.

Thanks to SOSS it will be possible to feed slapgrid* with various tasks, which
will allow to test different scenarios.

Master will be simulated in test, and it will be used to give tasks to
slapgrid and read its responses.

Override some methods and modules in order to get list of what would be done,
instead of having it done.

Thanks to this blackbox testing is much easier.

It makes blackbox testing much easier, as own OS implementation can overridden
in tested class.

createWithOwner requires User object, not string representing username.

It makes testing much easier.

This theme is really complex, and having beautiful buttons which are submitting
form is worse then just have working links without side effects.

It is important to cover a case when Software Release get archived, but it is
still used on Computer.