Test theory I/O
Standardise the format of vertex and edge data
quanto-xml-to-json: assume *.ruleset files are rulesets
quanto-xml-to-json: allow rule userdata to be absent
Convert example graphs and rulesets to JSON
Fix old GUI to work with new standardised graph formats

There's a complete hack in the core to support the old method of
updating vertex data, but that will go when the old protocol/interface
is removed.