Move every file from plugins into zshrc.d as well as all bigger blobs in
the zshrc into their own files there.
Some stuff is still in there that I am not all too sure where it
belongs. TODO: Move.
Because all external plugins are now sourced over a symlink I had to
create a fork of fzf-tab for now that supports that.
See: https://github.com/Aloxaf/fzf-tab/pull/153
