Copyright for pytest-salt source package in Lunar

Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
Source: https://github.com/saltstack/pytest-salt

Files: *
Copyright: 2015-2016 SaltStack Team
License: Apache-2.0

Files: debian/*
Copyright: 2018 Benjamin Drung 
License: Apache-2.0

License: Apache-2.0
 On Debian systems, the full text of the Apache-2.0 license
 can be found in the file '/usr/share/common-licenses/Apache-2.0'.