[PATCH v2] Add SELinux policy for virt

Sorry for the long delay. This is our first request to ship a policy for multiple selinux stores (targeted, mls and minimum). Changes: * Replace all selinux-policy-%{policytype} dependencies with selinux-policy-base * Add Ghost files representing installed policy modules in all policy stores * Rewrite policy compilation script in python * Compile the policy module twice (1 version for targeted/minimum - with enable_mcs, and 1 for mls - with enable_mls) * Manage policy (un)installation using triggers based on which policy type is available The new policy was only tested in "targeted" mode so far and we'll need to make sure it works properly in "mls". As for "minimum", we know it will not work properly (as is the case of the current policy) by default (some other "contrib" policy modules need to be enabled). I'd argue there is no point trying to get it to work in "minimum", mostly because it (minimum) will be retired soon.