cobald namespace package

[maxfischer2781]

The cobald top-level namespace only exists to host sub-packages, but does not contain any functionality. Sub-packages mostly rely on each other via their APIs, not implementation. This setup matches a namespace package, which allows spreading sub-packages over multiple repositories/distributions.

• convert cobald to a namespace package
• document how to add sub-packages to the cobald namespace

Using a namespace package would allow keeping the daemon implementation in the cobald namespace but separating it (see issue #10).

[maxfischer2781]

Closed by #26 .