gnukhata-core debian

This package was initially a update for gnukhata-core-engine which is already
in Debian, but due to its non maintainance from a long time, I decided to make
this new source package from scratch. I have talked with the maintainer of
currently gnukhata-core-engine and they agreed that with this package in debian
archive they will remove the older gnukhata-core-engine from the archive

See https://lists.debian.org/debian-python/2018/10/msg00012.html for the
agreement of the maintainers.

This package is Python2 as was gnukhata-core-engine. Upstream has no plan to
make a Python3 version, but we intend to raise the question and we hope a
Python3 release will appear before the end of life of Python2 in Debian.  In
the meantime, it's better to have an up-to-date release of gnukhata-core.
