Provide explanation of dangling indices, fixes #26008#26999

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geekpete merged 2 commits intoelastic:masterfrom

geekpete:master

Jan 22, 2018

Commits on Oct 17, 2017

Provide explanation of dangling indices, fixes #26965
geekpete
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Commits on Dec 21, 2017

updates to suggested wording and minor typo fix.
geekpete
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