Serve analyses files via sendfile & protected them

This requires tomcat to use an appropriate connector (nio or apr). In
any case, sendfile with tomcat is only actually used if you have

    grails.plugins.sendfile.tomcat = true

Otherwise, it falls back to send the file in the controller.
Add  unit tests for AnalysisFilesController
Merge pull request #59 from thehyve/protected_analyses_results

Serve analyses files via sendfile & protected them