Cyclic object graph support - round 2.

This release adds support for cyclic object references inside RION Table fields, both at the row level and column value.

This release also fixes a few minor bugs - one of which was in RION Table reading - when reading Table fields inside object graphs. Another bug was in the RionReader's functionality to read RION Extended fields using a Short encoding. A third bug was in the RionToHexConverter's conversion of RION Extended fields to hexadecimal format.