update default Central discovery URLs in JBT to point to Final / GA URLs instead of last dev milestone

PRs for fixing the pom in the 4.1.x branch and adding more reminders so we don't forget to update in BOTH places next time:

https://github.com/jbosstools/jbosstools-central/pull/142 (41x)
https://github.com/jbosstools/jbosstools-central/pull/144 (master)

These do not block Final/GA release.

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Effect of this bug is that users of JBT 4.1.0.Final will (at some point, if we release a dev milestone of 4.1.1.x) see 4.1.1.x discovery content rather waiting until 4.1.1.Final is released to see an update to their Discovery content.

But, since we duplicate the content in http://download.jboss.org/jbosstools/updates/stable/kepler/jbosstools-directory.xml to http://download.jboss.org/jbosstools/updates/development/kepler/jbosstools-directory.xml this should not affect anyone adversely, and we can fix this for 4.1.1 (if there's to be a 4.1.1).