"No hits found" in blast search breaks hash sorting

[bretonics]

When a crispr sequence has no matching sequences in search sequence, then nothing is stored in hash. This causes an "undefined value" error when sorting unique identities for each match.

• [x] The integrity of the 'targets' hash must be checked to include all crispr occurrences (keys)
• [x] If no matches found for crispr, then store appropriate info in attributes

[bretonics]

When using BLAST+, it will be better to use BioPerl's module's StandAloneBlastPlus to call blast and SearchIO to parse the results.

This in theory should allow identification of query sequences producing "no hits", setting values accordingly, and writes XML files as default.