101 Fix scaladoc warnings - fixed in streaming but leaving the rest as i...

...s. This is a known bug that will be fixed in a later version of Scala. Minor cleanup of build and addition of sbt unidoc plugin
Add: Fixed broken links in API documentation
Add: refactored RDDFunctions and DStreamFunctions - merged saveToCassandra overloaded methods into a single method with defaults.
or sth like this ;)