Using LFs in the Rackspace examples POM and updating the UploadDirectoryToCDN example

* Adding ability to upload to cloudfiles-uk
* setting configuration values via system properties
* making BlobDetail fully immutable
    
Follow-up to 089bc285

"Tested" as follows:
```
mvn clean package
mvn dependency:copy-dependencies "-DoutputDirectory=target\lib"
java -cp target\rackspace-examples-1.0.jar;target\lib\* org.jclouds.examples.rackspace.cloudfiles.UploadDirectoryToCDN foo bar target baz
Uploading target to baz
(fails since credentials are invalid)
java -cp target\rackspace-examples-1.0.jar;target\lib\* -Djclouds.io-worker-threads=5 -Djclouds.provider=cloudfiles-uk org.jclouds.examples.rackspace.cloudfiles.UploadDirectoryToCDN foo bar target baz
Uploading target to baz
(fails since credentials are invalid)
```