added more tests for VDiskFileInputStream and VDiskFileOutputStream
Implemented a test that creates a big file and imports it.

On a Mac Book Pro Retina (new one) 16 GiB are imported in 3 minutes.
Merge branch 'master' of https://github.com/groggi/eth-jcd
created a new directory for slow tests and moved BigImportExportTest
Moved ch.se.inf.ethz.jcd.batman.util into .batman.cli.util