add validate-maven task to check maven dependencies [LUCENE-4354]

We had a situation where the maven artifacts depended on the wrong version of tika: we should test that the maven dependencies are correct.

An easy way to do this is to force it to download all of its dependencies, and then run our existing license checks over that.

This currently fails: maven is bringing in some extra 3rd party libraries.

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Migrated from [LUCENE-4354](https://issues.apache.org/jira/browse/LUCENE-4354) by Robert Muir (@rmuir), updated Sep 06 2012
Attachments: [LUCENE-4354_hacked_lucene_only.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4354/LUCENE-4354_hacked_lucene_only.patch), [LUCENE-4354.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4354/LUCENE-4354.patch) (versions: 11), [LUCENE-4354-dep-fix.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4354/LUCENE-4354-dep-fix.patch)

Start by reviewing the existing license checks and the attached LUCENE-4354 patches to locate the Maven build entry points. The task is done when Maven dependencies are fully downloaded, the existing license checks run over them, and incorrect or extra third-party libraries are identified or prevented.

Written by the indexing model from the issue text.