Use fixed AvalonDock with Extended Wpf Toolkit

Users of this library have reported that tey would like to use the libraries at dirkster99/AvalonDock together with the original Extended WPF Toolkit but were not able to do it because of collisions in the names of the binaries and versions. This page lists a sequence of steps that you can use to resolve this issue and use both, the libraries in this repository together with the original toolkit.