If Bam files cannot be found, make a better log message

[dankwart-de]

E.g.:

Did your bam file names match the pattern: ?
Do you need to adapt possibleControlSampleNamePrefixes...

[vinjana]

Really far fetched, but we could use Levenstein distance to suggest alternative files (like Google's suggestions), in case names were written incorrectly. :-D ... well maybe that would be overdoing it a bit.