Support for QSEQ parsing.

This relates to issue #389.  @audy, @wasade.

Added parse_qseq, QseqIterator, support in the factory for .qseq and .qseq.gz.  Added unit tests.

For Sequence ID, I am using: <machine_name>_<run_number>:<lane_number>:<tile_number>:<x>:<y>#<index>/<read>.  Example: CRESSIA_242:1:2204:1453:1918#0/1.  Do you agree?

I set qual_id to seq_id.  Do you agree?

One of the QSEQ record attribute is "filter".  I used "filter_" in the namedtuple "Record", what's your recommendation on name clashing?