guessing one bam or all inputs

[jorgeboucas]

https://github.com/dieterich-lab/DCC/blob/2afef01a06412b6b15a6bd49842bc706c0e648a4/DCC/main.py#L397

when no list of bams is provided only on his guessed and used as reference for all inputs in sample sheet

headers in LinearCount are then the rights ones though (can be dangerous if -B list is not sorted in the same order as the sample sheet).