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.

Cyclic object graph read/write - first draft

This version adds cyclic object graph writing and reading in preview. So far the RION Reference field has been implemented as an "RION Extended" field. Maybe that will change in the future. To make it clear when an "acyclic" or a "cyclic" object graph is written or read, the "read()" and "writeObject()" methods of RionObjectReader and RionObjectWriter have been renamed to "readAcyclic()", "readCyclic()", "writeAcyclic()" and "writeCyclic()". The "acyclic versions are faster, but can only write acyclic object graphs. To work with cyclic object graphs you must use the "readCyclic()" and "writeCyclic()" methods.

More null support, bug fixes and code cleanup

Improves the support for writing null fields in the RionWriter static write methods.
Removes several bugs related to reading and writing null fields.
Improved the unit tests
Cleans up the code a bit.

Improved support for writing null fields + bug fix

V. 0.9.0 contains increased support for writing null fields in RionWriter, a new method for checking if a given field is null in RionReader ( isNull() ), and a bug fix in RionWriter.writeUtf8() which serialized empty strings as UTF-8-Short null instead of UTF-8 with length 0.

v. 0.8.0 RionObjectWriterBuilder + RionObjectReaderBuilder added.

v. 0.8.0 RionObjectWriterBuilder + RionObjectReaderBuilder added.
These classes ease the configuration of RionObjectWriter and RionObjectReader. Now you can more easily remove fields from writing or reading. More configuration features will be added in future releases.

RionObjectWriter + RionObjectReader

This release adds the RionObjectWriter and RionObjectReader classes which can write Java objects (pojos) to RION and read RION to Java objects. This is very handy in some situations.

RION to Hex Converter Added

v. 0.6.0 adds a RionToHexConverter class which can convert RION to a structured hexadecimal (textual) format, for easier debugging of RION data.

v. 0.6.0 also adds a few extra methods to RionWriter for writing Array and Table fields easier.

0.5.3 Bug fix of reading RION UTF-8 fields into Java Strings

Apparently the methods that were reading UTF-8 fields into Java Strings did not pass the UTF-8 character set to the String constructor (in RionReader). This has been fixed now (issue #3)

0.5.2 First Release

This is the first usable release of RION Ops.
This version contains the basic functionality for reading and writing RION fields.
Later versions will include functionality for reading RION into Java objects, and
writing Java objects out to RION.