add SAM 1.6 to supported versions

[lbergelson]

We've implemented support for the major change in sam 1.6 which was support for long cigar operators. We should bump the version number of the SAMs we produce and accept.

We should check that we support the other changes listed in 1.6 before we do so.

[lbergelson]

#1194

[lbergelson]

A number of pr's related to this effort:

• Adding support for 0-length B arrays in SAM files to conform to 1.6 spec #1194 0 -length array support
• Changing htsjdk to produce sam version 1.6 #1211 - update htsjdk to support and produce 1.6
• Add support for Sam Header Readgroup Barcode field #1210 - RG barcode field
• Adding first class Description field to SAMSequenceRecord #1209 - SQ DS field
• Updating SAMTag and SAMTagUtils #1208 - adding new tag constants

[lbergelson]

We've discovered an issue with utf8 representation in sam that makes us non-compliant with 1.6. #1202

[magicDGS]

I think that also the following should be included:

• Add support for SQ-AN in SAMSequenceDictionary #956 - SQ AN field (included in samtools/hts-specs@da805be)