Consider forking pcdm as a Qt5 native display manager

Currently we are using `slim` which is doing its job, is mature (read: is no longer a moving target, which is a good thing!). But it is one of the few "alien" non-Qt components to our environment.

So, we may want to consider https://www.freshports.org/x11/pcdm/

Pros
* Qt native, can be made to use our QtPlugin and stylesheet
* Extremely few dependencies (e.g. xorg-minimal)
* No ConsoleKit
* Unlike with the current setup, you can safely kill the Dock and `sh` without being logged out of the session

Cons
* Messes around with the keyboard layout which we have already autodetected at that point
* We would have to fork and change it to become simpler
* autologin needs root password to be stored unencrypted in clear text... (maybe this is the reason why `slim` uses ConsoleKit)?