Increase the max allowed base Q score from 70 to 93

[clintval]

There are now error-corrected NGS technologies that can produce base quality scores Q60+. To make those technologies compatible with the Manta program, we need to increase the maximum allowed base quality score. A score of 93 is the maximum defined in the SAM spec v1 §4.2.3:

Base qualities are stored as bytes in the range [0, 93], without any +33 conversion to printable ASCII.

This is also the maximum for the HTSJDK project.