Remove java related parts from parquet-format

Since the java code generation part has moved to parquet-mr there is no reason (and it is misleading) to still keep these java files in the parquet-format repo and to release in a jar format.
The proposal is the following:
- Remove java code from the repository and update the pom.xml accordingly
- Keep the unit tests (to validate the PRs) but don't include them in the release. (We might release a separate `-tests` jar.)
- Release in a zip format instead of a jar. The zip would contain all the documentation and the `parquet.thrift` file
- Also move the [dremel paper](https://github.com/apache/parquet-mr/tree/master/doc/dremel_paper) from parquet-mr to parquet-format
- Update the [How to release](http://parquet.apache.org/documentation/how-to-release/) doc

**Reporter**: [Gabor Szadovszky](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=gszadovszky) / @gszadovszky
**Assignee**: [Gabor Szadovszky](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=gszadovszky) / @gszadovszky

_{**Note**: *This issue was originally created as [PARQUET-2007](https://issues.apache.org/jira/browse/PARQUET-2007). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

Start by inspecting the repository's Java sources and pom.xml, then review the existing unit tests and release configuration. Check the parquet.thrift file, the dremel_paper location in parquet-mr, and the How to release documentation; done means the repository and release contents match the listed proposal without Java artifacts in the main release.

Written by the indexing model from the issue text.