This was broken by some missing closing tags in 0bea4a50

Closes #179.

preferLocalBuild does not in fact prevent substitution.

This prints the references graph of the store paths in the graphML
format [1]. The graphML format is supported by several graph tools
such as the Python Networkx library or the Apache Thinkerpop project.

[1] http://graphml.graphdrawing.org

`fetchurl` will now throw if given an `md5`, and the hashes have generally
been upgraded to avoid it and use `sha256` as a default. This updates the
documentation examples in the manual accordingly.

For example, this prevents a "kvm" build on machines that don't have
KVM.

Fixes #2012.

Update docs to describe how s3:// URLS does in fact support endpoint, region, and profile for upload

and make it more copy-pastable.

Fixes #2396.

release notes: note that the multi-user installer is available but not selected for Linux with systemd, and the bug about selinux

Use sh <(...) syntax for installation to preserve stdin and prompting

also update installation docs to account for changes in multi-user selection

shell.nix defines the install prefix as $(pwd)/inst