Use dbus-client-gen testing infrastructure

[mulkieran]

It uses Hypothesis to generate representative spec files; in this library we're still stuck with the old style of a fake example.

[mulkieran]

@lleshchi: The idea is that you would rewrite the tests to use the same Hypothesis testing infrastructure that is used in dbus-client-gen. You would have to grab a file from that library, as the infrastructure I wrote is not yet ready to be published.

[mulkieran]

Removing from any specific calendar...