Co-Authored-By: Matthias Schiffer <mschiffer@universe-factory.net>

This copies the code from web-admin and uses it to create a neat
cli-accessible summary about a node

This could also be extended or possibly have all the data the status
page has

Co-Authored-By: Matthias Schiffer <mschiffer@universe-factory.net>

This should not convert JSON to a Lua table and back, as this loses the
distinction between arrays and objects, but as our site.conf is defined in
Lua anyways (for now), this can be fixed in a later revision.

[Matthias Schiffer: rename to gluon-show-site, rebase]