[Enhancement] add NTP remote server OVAL to shared

- Move NTP remove server check to shared directory
- Enable for RHEL 6 & 7 and Fedora
Merge pull request #333 from redhatrises/ntp_remote_server

[Enhancement] add NTP remote server OVAL to shared
[Enhancement] [RHEL/6] Set GNOME Login Inactivity Timeout:
* change rule ID in XCCDF & profile references to use OVAL ID,
* add remediation
[Enhancement] [RHEL/6] GNOME Desktop Screensaver Mandatory Use:
* change rule ID in XCCDF & profile references to use OVAL ID,
* add remediation
[Enhancement] [RHEL/6] Enable Screen Lock Activation After Idle Period:
* change rule ID in XCCDF & profile references to use the OVAL one,
* add remediation
[Enhancement] [RHEL/6] Implement Blank Screensaver:
* change rule ID in XCCDF & profile references to use the OVAL one,
* add remediation
[RHEL/6] Condense check for GConf2 package installed in RHEL-6 gconf remediations
Merge pull request #334 from iankko/rhel6_gconf_remediations

[Enhancement] [RHEL/6] Add RHEL-6 gconf rule's remediations