JCLOUDS-225: Setting 'clean install' as default release preparation goals

Partially reverts 8cc82b0. Thanks to @iocanel for hunting that down!
Upgrade jclouds-karaf to Guava 15.0-rc1
Upgrade to Guava 15.0

Release notes:

https://code.google.com/p/guava-libraries/wiki/Release15
JCLOUDS-301: work around OOM with blobstore list
JCLOUDS-387: Removing DISCLAIMER file now that jclouds has graduated
Remove more incubator references

Fixes JCLOUDS-388.
Correct JClouds -> jclouds typos
Correct Jclouds -> jclouds typos
Correct JClouds -> jclouds typos
[JCLOUDS-189] Upgrade to Karaf 2.3.2. Explicitly specify jclouds feautre to add to feature repo. Use Karaf's 2.3.x pax-exam support.