Agnostic

As per PR #14, this adds the `vcsh setup` and `vcsh where` commands, with necessary documentation. It also enables the sourcing of `./.config/vcsh/config`, which `vcsh setup` will automatically create with the `$VCSH_BASE` and `$XDG_CONFIG_HOME` variables set to `$(pwd)` and `$(pwd)/.config` respectively, thus enable "agnostic" use of `vcsh` from the folders with the a `./.config/vcsh/config` file.

It's a work in progress, and probably needs more testing, but I think it's a good way to go about doing this.