* Adds startTupleField/startStructField, makes pattern in print targets less verbose
* Makes some enums into strings
* Start/finish renamed to begin/end
I feel bad changing this, but I don't know why I named them this way in the first place.
Begin/end is consistent with the json API, and with other APIs in the wild that follow this pattern.
Better to change now than later.
339b628d4c