Genomic reference transcript mappings

Support genomic references in the mapping database. At the moment, this is
only tested with mtDNA genes, but should in clear the way for NG_ mappings
as well.
Mappings for mtDNA genes can be added to the database using the command line
tool mutalyzer-mapping-import.


git-svn-id: https://humgenprojects.lumc.nl/svn/mutalyzer/trunk@635 eb6bd6ab-9ccd-42b9-aceb-e2899b4a52f1