Changed XML element names to camel case.

This is more in line with the JSON config files and sticks closer to
identifier naming rules in various languages, making results easier to
handle.
Tweaked how index structure is reported.

Made structure more similar to configuration file and index metadata
file; didn't report empty values; added complex field display name and
description.
Added includetokencount param. to report token count in matched docs.

This can be used to determine the size of a subcorpus, for example.