Load N sequences in Mussa::load

Fix for ticket:240.

Mussa would not load the sequences because the .muway file would
declare that 0 sequences existed. Since the Mussa:load code needed to
know the number of sequences to load the sequences, it failed.

The new version of the load sequence code, reads the sequences in
until there are no longer any sequences to read. At that point, the
number of sequences is the_seqs.size() and therefore is no longer
dependant on the muway file.