Storage refactor

@stephanfowler kindly pointed out tha `JSON.stringify` takes all types (not just `object`s), ss refactored to remove the annoying type appending.

However, to make this backward-compatible would take a load of spaghetti code, so I've removed it all, effectively clearing the local storage

Only real loses are states of auto refresh and trailblocks, which I think is an acceptable cost for easier code (whatever you do, don't tell @commuterjoy)