Release management: resolve the circular dependency freeze problem

[hartym]

There is a problem with the release process, which is not very bad, but still may become in the future.

We have bonobo[X] (here X is one of docker, sqlalchemy, selenium, etc) depend on bonobo-X.
But bonobo-X depends on bonobo, too.

So we have to find a way to freeze the dependency, because obviously it's hard to be in the future at release time.

Maybe we should force usage of bonobo[X] (which was the favored way while discussing with people) and make sure the freezing is correct this way (freeze version of dep in bonobo for bonobo-X, which means release bonobo-X before bonobo while doing maintenance, and unfreeze bonobo in bonobo-X, that should only rely on bonobo "stable" (and anyway, it wont be encouraged to install extensions this way))