Upgrade versions

- jclouds from 1.5.2 to 1.5.4
- surefire from 2.12.3 to 2.13
- ant from 1.8.2 to 1.8.4
- testing from 6.7 to 6.8
- mockito from 1.8.4 to 1.9.5
- removed spring version (unused)

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Replaces Andrew's https://github.com/brooklyncentral/brooklyn/pull/398, by extracting the groovy upgrade from it and also upping the jclouds+surefire versions (since his pull request was originally submitted), and removing the unused spring version.