Provide example to write/save your own object (without thrift, avro, protoc)

I am studying parquet and found that it is not so easy to grasp the basic mechanism for writing/reading your own objects to a parquet file when you are not using protocol buffer, avro or thrift.

So my wish is to have a module that cover this topic.
I think for educational purposes it may have some value as it would help people get into the code.

I did the exercice, the code is here:
https://github.com/nromanetti/parquet-mr/tree/master/parquet-manual

**Reporter**: [Nicolas Romanetti](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=nicolasr)

_{**Note**: *This issue was originally created as [PARQUET-420](https://issues.apache.org/jira/browse/PARQUET-420). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Start by reviewing the parquet-manual example linked in the issue and compare it with the current parquet-java layout. Identify where an educational module or example would belong, and consider the issue complete when it clearly demonstrates writing and reading custom objects without Thrift, Avro, or Protocol Buffers.

Written by the indexing model from the issue text.