separate vim config from nvim config again and simplify it

Separating vim's config from neovim's config simplifies the deployment
of lua for neovim's configuration. At the same time, clean up current
neovim config by removing all outdated options and options with equal or
even better defaults. Furthermore, the 'old' vim configuration should be
kept as-is to ensure compability with older systems if needed.

setup.sh

@@ -44,18 +44,19 @@ link()
 link pam_environment ~/.pam_environment
 
 # application-specific config
-if installed nvim || installed vim; then
-	echo "Setting up nvim:"
-
-	mkdir -p ~/.config
-	link config/nvim ~/.config/nvim
-
-	echo
-fi
 if installed vim; then
 	echo "Setting up vim:"
 
 	link vimrc ~/.vimrc
+	link vim ~/.vim
+
+	echo
+fi
+if installed nvim; then
+	echo "Setting up nvim:"
+
+	mkdir -p ~/.config
+	link config/nvim ~/.config/nvim
 
 	echo
 fi