StringFields name is unintuitive and not helpful [LUCENE-4369]

There's a huge difference between TextField and StringField, StringField screws up scoring and bypasses your Analyzer.

(see java-user thread "Custom Analyzer Not Called When Indexing" as an example.)

The name we use here is vital, otherwise people will get bad results.

I think we should rename StringField to MatchOnlyField.

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Migrated from [LUCENE-4369](https://issues.apache.org/jira/browse/LUCENE-4369) by Robert Muir (@rmuir), updated Sep 18 2012
Attachments: [LUCENE-4369.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-4369/LUCENE-4369.patch)
Linked issues:
- #2440
- #4865

Start by comparing StringField and TextField, then review the linked issues #2440 and #4865 and the referenced java-user thread about analyzers. The proposed outcome is to decide whether StringField should be renamed to MatchOnlyField and account for the naming change across the affected API.

Written by the indexing model from the issue text.