port should be specified through -p (or --port) command line option

So config file now contains BLAST specific settings only.  Whereas, port was
meant for the self hosting server.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Settings derived from configuration file are now local to an App object.

One process should be able to run multiple SS instances now.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>
Just raise IOError if no BLAST database were found by scan_blast_db.

Old, broken behaviour was to interactively guide the user through creation of
BLAST database. Broken at the expense of bad code. Hence removed.  Will
consider re-adding it later.

Signed-off-by: Anurag Priyam <anurag08priyam@gmail.com>