Include dwmipcpp as a library in cmake and config files, so it can be built
automatically. The configuration of dwmicpp was added to match that of i3 and
bspwm to maintain the same cmake workflow and style.
Since APP_VERSION is different for every commit and almost all file
include settings.hpp, the whole project has to be rebuilt for every
commit. With this, hopefully, this can be greatly reduced and only
changed files need to be rebuilt. This will also help ccache