poll-mirrors.pl should let you check multiple paths on each mirror [LUCENE-5108]

Idea spun off from #6168 based on sarowe's experience dealing with mirrors that are only partially updated (this is all very doable, but requires some major rewriting of hte logic flow in the script, so i wanted to break it out into it's own issue)...

> There's a separate (but maybe related to what you want to do here) issue with poll-mirrors\.pl - when Shalin did the 4\.3\.1 release, he didn't upload all of the artifacts at once, and as a result, the script reported that "the release" was on all mirrors, even though some parts weren't there yet, rendering the information useless\.
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> Maybe the script could take one or more suffixes, so that it could find any number of things on each mirror, and report how many mirrors have **all** of them?

...

> > does it really matter "what percentage have X and Y?" or just "what percentage have X? what percentage have Y?"
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> The way I've used that script, the question has been: Can I announce that the release is available? This is answered when all parts of the release are downloadable from some threshold percentage of mirrors, thus "what percentage have X AND Y"\. As you say, though, this could be performed by running the script in multiple terminals with different paths\. One goal of the script, though, was having just one place to go to get the answer to the question (thus lumping Maven in there too)\. Maybe the script could be (eventually - shouldn't block the nice changes you've made here) changed to allow multiple -path options, and print a number instead of a "\." for presence or "X" for absence, representing how many of the files are downloadable at each mirror: "0", "3", etc\.

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Migrated from [LUCENE-5108](https://issues.apache.org/jira/browse/LUCENE-5108) by Chris M. Hostetter (@hossman)

Start by locating and reading poll-mirrors.pl, then run it against the existing mirror checks to understand its current reporting. Clarify whether multiple paths should use AND semantics and how counts should be displayed; done means the script can check multiple release artifacts per mirror and identify mirrors containing all of them.

Written by the indexing model from the issue text.