BLASTN test designed to give multiple strong hits for the query

This checks the max-hits option works on both tabular output
(using -max_target_seqs) and plain text (using -num_alignments
and -num_descriptions) to cope with NCBI BLAST+ 2.2.27 which
broke the original behaviour (allowing -max_target_seqs to be
used for all output file formats). See issue #55.

Note this has to use a BLAST database since -subject gives
pairwise results and thus ignores the output limits.