Better descriptions on chromosome

For UD slices we also generate g. descriptions on the chromosome reference. We
now also apply the roll rule there and use correct ranges and sequences on the
reverse strand. Fixes #75.


git-svn-id: https://humgenprojects.lumc.nl/svn/mutalyzer/trunk@495 eb6bd6ab-9ccd-42b9-aceb-e2899b4a52f1