Get args from multiple types at once

[Chris Warburton]

We're currently looping through each type in our sample, e.g.

    function allArgs {
      completeTypes | while read -r TYPE
      do
        echo "$TYPE" | "$isabelleTypeArgs"
      done | sort -u
    }

The problem is that "$isabelleTypeArgs" takes a little time to warm up,
which happens for every single name. This accumulates to become pretty
slow.

To fight this, we should read in and write out JSON array of types. That
way, it only has to be invoked once per sample.