Move Python modules from 'share' to 'bcftbx'.
bcftbx: add __init__.py files to make into a package.
bcftbx: update Python test modules to accommodation restructuring.
bcftbx: rename 'bcf_utils.py' to 'utils.py'.
bcftbx: fix modules and tests that were broken by renaming 'bcf_utils' module.
bcftbx: more fixes to modules to deal with renaming 'bcf_utils' to 'utils'.
Update Python programs to accommodate restructuring of library modules.
Updated READMEs to reflect relocation of Python modules to 'bcftbx' package.
Updated ChangeLog.