Added masking to Subtraction 2

Streamlined code

Moved all code for primer design into repo

github.com/evolbioinf/prim

Parallelized makeFurDb

Iterative fur

Fixed excess deletion in second subtraction

Added stand-alone cleanSeq

New intersection and subtraction steps

The old checking steps are rewritten leading to large improvements in
template yield.

Include makeFurDb and three scripts

The three new AWK scripts automate steps in primer design:

- fur2prim.awk - convert fur output to primer3 input
- prim2fasta.awk - convert primer3 output to FASTA files
- checkPrim.awk - check primers using BLAST

Neighborhood check with blastn

Added -U, changed window length, revised Tutorial