issue 71 - RHEL7 STIG CCI-000017, inactivity expiration

- added CCE
- Moved OVAL into shared
- Updated for RHEL7, bumped OVAL version
Issue 74 - RHEL7 STIG - logon banners

Resolves https://github.com/OpenSCAP/scap-security-guide/issues/74

- Added CCEs
- Added OVAL to shared
Issue 75 - limit concurrent sessions

- Added CCE
- Updated OVAL location
- Updated OVAL CPE

resolves https://github.com/OpenSCAP/scap-security-guide/issues/75
Merge pull request #352 from shawndwells/issue75

Issue 75 - limit concurrent sessions
Merge pull request #350 from shawndwells/issue71

issue 71 - RHEL7 STIG CCI-000017, inactivity expiration
Merge pull request #351 from shawndwells/issue74

Issue 74 - RHEL7 STIG - logon banners