removed attoparsec-iteratee dependency

Seemed to cause dependency problems.  While at it, updated the imports
from attoparsec to silence some warnings.
removed Bio.Genocall.Matrix

Replaced the hand-hammered matrix and vector with better implementations
from the Vec package.  Cleaned up some code involved in it.
added Avro container writer

Added a very primitive container file writer along with some fixes.
Right now, codecs are not supported and the splitting into blocks is
rather stupid.  However, such container files have been fed to a C++
program, which actually understood them!