WordBreakSpellChecker: suggest in order of minimum term frequency [LUCENE-6237]

When the Word-Break Spellchecker breaks a term into more than once, currently the results are ordered first by the number of breaks, then by the _maximum_ frequency of the new terms. But in many cases, it seems better to sort secondarily on the _minimum_ frequency.

See this thread from the users' list: http://lucene.472066.n3.nabble.com/alternativeTermCount-and-WordBreakSolrSpellChecker-combination-not-working-tp4185352p4185489.html

As a follow-on, we should expose this new configuration detail for solr users, possibly making it the default.

---
Migrated from [LUCENE-6237](https://issues.apache.org/jira/browse/LUCENE-6237) by James Dyer (@jdyer1), 1 vote

Start by locating the WordBreakSpellChecker implementation and the Solr spellchecker configuration path, then review the linked users-list discussion for the intended ordering. Done means split-term suggestions use minimum term frequency as the secondary ordering and the Solr configuration behavior is explicitly decided and covered.

Written by the indexing model from the issue text.