explain() cursor field should store index used and type of scan in separate fields

The cursor field for an explain() may look like this:

Rather than storing all of this information in the same field, we could break it up in to separate fields:

{ "cursor" : "BtreeCursor",
"index":

,
"iterators": ["reverse", "multi"]
}

Not sure on the name of the last one, but you get the idea.