Common Print Dialog Backends (CPDB) 2.0b6 release!

Hi,

I have done the 2.0b6 release of the Common Print Dialog Backends now!

This is mainly for snapping the CPDB CUPS backend, so that we can complete the 
fully snapped printing stack for Snap-only distros like Ubuntu Core Desktop, for 
providing the printing stack as Snaps in a future version of the standard 
Ubuntu, and perhaps even including the CUPS backend in the CUPS Snap so that 
they are always in sync.

In addition we have fixed a lot of crasher bugs since 2.0b5 and so all these 
fixes are now in a release.

And there are more improvements and fixes. See our release announcement:

https://openprinting.github.io/Common-Print-Dialog-Backends-Second-Generation-Sixth-Beta-Release/

Please make sure to update both cpdb-libs and cpdb-backend-cups. And check out 
the API changes in the announcement.

    Till