Moved file input/output functions into io submodule

The existing xml parsing and data archiving functions are all fileio
functions, so it makes sense to put them in their own io submodule. I've
also added functions to convert various binary config files to numpy
arrays, using qcdutils to do so. Some changes were needed in qcdutils to
make it compatible with Python 3, and I've stripped out various
functions that are used by the main function but are otherwise not
needed.
Removed outdated section of pyQCD package docstring from __init__.py
Removed outdated imports from some of the core modules
Renamed parallel functions parmap and spawn to _parmap and _spawn
Changed credit for parmap to spawn to specifically refer to these functions
Fixed create_lattice function in Simulation class

Now passes arguments to Lattice constructor in the correct order.