Nstonehouse/repo split/er recorder

The *.json files are included for expected results, if they exist already. They're intended for generateExpectedResults==false (once they've already been generated).

If the ERs are missing, it's a problem for any ER-dependent tests. Right now there is a warning if they are missing ('WARN [watcher]: Pattern "..." does not match any file'). Unfortunately this error is mistaken if there are no ERs for that test suite. I can look into a more elegant way to exclude these files to ignore that warning.