ENH: add parcel property types (fixes #109)

- assists in decoding what the binary IO content means

ENH: use label instead of bool for the KinematicParcel active state (fixes #111)

- avoids internal padding of the data structure and simplifies
  downstream use.

ENH: make particle sizeofFields public (fixes #110)

Also fixes #108 (missing faceI and stepFraction entries) which had
also been fixed in the upstream as well.