blastall -> blast+; syntax via NCBI's legacy_blast script

Switch to modern blast syntax.
They pass:
```
N       sum     max     filename
35      61355   4449    /mnt/work/trinity_out_dir/Trinity.fasta
```
```
root@ip-10-231-135-216:~/khmer-protocols/mrnaseq#  grep -c "zinc transporter" /mnt/blast/trinity.x.mouse                                    
24
```