removed unused imports
New version: 0.4.15
doc: make the documentation generation independent of hawkey the python module.

This is so readthedocs.org work. Uses the same approach as DNF commit fce01f9.
Goal: listing unneeded packages.

With py bindings and tests.

Related: RhBug:963345
iutil.c: simplify queue2plist() implementation.
goal: hy_goal_write_debugdata() takes target dir parameter.
cleanup: tweak declarations in pycomp.h.
py: fix: certain string assignments should raise TypeError, never SystemError.
py: Package: all string attributes are in Unicode (RhBug:1093887)