terminal: Move bash and zsh into config directory

With the power of dotter for dotfile management we can move the files we
want to link anywhere in our repository.

So finally we're making use of it to keep the bash config files in the
`terminal/.config/bash` directory, as well as removing the leading dot
from both the zsh configuration files.

terminal/.config/zsh/zshenv

@@ -0,0 +1,15 @@
+#!/usr/bin/env zsh
+#
+
+# load zsh specific env vars
+if [ -d "$XDG_CONFIG_HOME/zsh/env.d" ]; then
+  for _env in "$XDG_CONFIG_HOME/zsh/env.d"/*.zsh; do
+    . "$_env"
+  done
+  unset _env
+fi
+
+# add XDG_CONFIG_HOME/zsh/completions to fpath
+# zsh uses it to look for completions; throw all
+# completions in these dotfiles in there
+fpath=("$XDG_CONFIG_HOME/zsh/completions" $fpath)