Handle empty hash values on packages

If a packages does not provide a sha256 hash we need to generate one.
Use the package name and version for this. This issue appears for
example on older precise boxes where no package updates have happened.

Include two package lists generated with aptcacheexport as test cases.
Fix test data file loading

Simple path detection not working on CI host. Use the path from the
current file to construct the proper path for the data files

Signed-off-by: Christoph Kassen <c.kassen@telekom.de>
Merge pull request #26 from TelekomCloud/bugfix/package_import

Handle empty hash values on packages - Merging now to create a release for packaging.