option to ease transition for some users
My data has top level arrays stored as strings (JSON encoded).  This
option allows the user to tell vogels to convert these strings to sets
on the fly.
Merge branch 'json' into dev

* json:
  option to ease transition for some users My data has top level arrays stored as strings (JSON encoded).  This option allows the user to tell vogels to convert these strings to sets on the fly.