Dictionary-based lemmatizer [LUCENE-6254]

The only way to achieve lemmatization today is to use the SynonymFilterFactory. The available stemmers are also inaccurate since they are only following simplistic rules.

A dictionary-based lemmatizer will be more precise because it has the opportunity to know the part of speech. Thus it provides a more precise method to stem words compared to other dictionary-based stemmers such as Hunspell.

This is my effort to develop such a lemmatizer for Apache Lucene. The documentation is temporarily placed here:
http://folk.uio.no/erlendfg/solr/lemmatizer.html

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Migrated from [LUCENE-6254](https://issues.apache.org/jira/browse/LUCENE-6254) by Erlend Garåsen
Attachments: [LUCENE-6254.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-6254/LUCENE-6254.patch)

Start by reading the linked LUCENE-6254 documentation and the attached LUCENE-6254.patch to understand the proposed dictionary-based lemmatizer. Compare the proposal with Lucene's current analysis components and determine the required integration points before defining what a complete implementation and its validation would involve.

Written by the indexing model from the issue text.