WIP TIKA-1292: Fixing the MimeTypes class to consider "clusters" of magics by priority

This changes MimeTypes class to consider "clusters" of magics instead of "first found" to resolve priority clashes like those described in issue.

This is WIP, as the tika-core module builds okay, but tika-parsers module has one test failure, that am somewhat uncertain why. I'd like someone to take a peek and comment. Thanks.

Issue
https://issues.apache.org/jira/browse/TIKA-1292