NUTCH-3033 Upgrade Ivy to v2.5.2

[lewismc]

PR for https://issues.apache.org/jira/browse/NUTCH-3033
I was having trouble locally resolving the Ivy version to 2.5.2… I can’t yet figure out why 2.5.1 was being used. I’ll check out the CI log and see if the newer version is used.

[lewismc]

OK so it looks like the newer Ivy version is being used just fine. The build did however fail with the following

Caused by: java.lang.RuntimeException: Multiple artifacts of the module io.netty#netty-transport-native-kqueue;4.1.84.Final are retrieved to the same file! Update the retrieve pattern to fix this error.

… investigating.

[lewismc]

Hmmm, I upgraded to 2.5.1 and the CI runs just fine. Looks like there is some regression/additional configuration required with 2.5.2. I’m asking the question over on ivy-user@ mailing list.

[lewismc]

After lots of trial and error I think I cracked this one. Ultimately there were several places where the optional (-[classifier]) element has to be added to the ivy:retrieve pattern.
This wasn’t particularly intuitive as the ivy documentation is somewhat lacking in this regard however @bodewig pointed me in the right direction on the ivy-user@ mailing list. Thank you for that @boedwig.

This PR is ready for review.

[sebastian-nagel]

+1 Looks good! Everything compiles, unit tests pass.

[lewismc]

Thanks @sebastian-nagel 👍