Various dependency clean-ups

Attempts to make the POM files a more accurate representation of what each module is actually using, and to standardise on placing versions in the root POM *only* (in the `dependencyManagement` section)

Testing: full unit test run; started Brooklyn and deployed MySQL+Tomcat cluster to localhost
This shouldn't be imported! It's because of incorrect imports such as `com.beust.jcommander.internal.Lists`.
I'll create a PR, and tidy that up now. Can you then delete this dependency, before it gets merged?