This PR changes the way to download the test data into the VM.
Although it does not use a disk image as suggested in one
of the review, it does not clone the entire repository, but
a simple tar.gz file that holds the data which will be
distributed into the directory structure.
This way, the amount of data needed to be downloaded dropped
from approximately 50MB to below 2MB.
Also, the existing test suites were adapted to this situation.
Lukáš Růžička