Major fixes for bundling/unbundling code

- Fix process waiting in create_(un)bundle_pipeline
- Fix file handle closing in create_(un)bundle_pipeline
- create_(un)bundle_pipeline now return one-way Connections instead of Queues
- BundleParts now have (and require) sizes
- A few other minor fixes
Minor fixes for BundleManifest
Add new euca-bundle-image implementation
Shut off BundleManifest XML Comments
Add more BundleManifest logging
Minor BundleImage improvements
Clean up after IOError'd pipelines better
PEP8 cleanup
Use multiprocessing instead of os.fork