Add an option to skip optical duplicate detection
Add an option to skip optical duplicate detection

It may be desirable (or necessary, time-wise) to skip this step when
there are a *lot* of duplicates.  The duplicate detection loop slows
down quick when the groups under consideration get too large.

Note that this will affect the accuracy of the library size estimate.

nh13/picard,alecw/picard,annkupi/picard,broadinstitute/picard,nh13/picard,nh13/picard,annkupi/picard,alecw/picard,broadinstitute/picard,broadinstitute/picard,annkupi/picard,alecw/picard,broadinstitute/picard,alecw/picard,broadinstitute/picard,annkupi/picard,nh13/picard