Fixes Facts string comparisons in CentOS 7

- CentOS Project has adopted a new rule for versioning numbers. The major number
  matches the RHEL major number, but the minor number is generated from the
  release date. For example, CentOS 7.0.1407.
- Adds Support for Scientific Linux.

Change-Id: I3220206aa01b9f5c838e524b3fec723c92435153
Closes-Bug: 1338777
Signed-off-by: Gael Chamoulaud <gchamoul@redhat.com>