Merge pull request #4 from wtsi-npg/devel

devel
added sanger168_7.tags for 7-base index reads
use length of index read from tag0 bam file rather than length of tag in
decode metrics file to derive barcode file, added new tests and test data
add changes for release 56.6
added tag_sets data sub-directory to MANIFEST
Merge pull request #18 from srl147/devel

use length of index read from tag0 bam file rather than length of tag in
decode metrics file to derive barcode file, added new tests and test data