refpolicy: new package

refpolicy: new package

The patch is for adding selinux reference policy (refpolicy).
It is a complete SELinux policy that can be used as the system policy
for a variety of systems and used as the basis for creating other policies.

Signed-off-by: Adam Duskett <Adamduskett@outlook.com>
Tested-by: Matt Weber  <matthew.weber@rockwellcollins.com>
Acked-by: Matt Weber  <matthew.weber@rockwellcollins.com>
[Thomas:
 - add entry to DEVELOPERS file
 - remove redundant dependencies
 - drop unused REFPOLICY_PYINC option
 - use SPDX tag for license
 - minor formatting fixes.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>