[RHEL/6, RHEL/7] Update 'Disable Bluetooth Kernel Modules' rule guidance

* drop mention of net-pf-31 from XCCDF description since it's just alias
* drop calling net-pf-31 macro from OCIL
* move the OVAL check to shared (add RHEL-7 platform support, update test attestation)
* update OVAL check to use 'OR' operator instead of 'AND'
* add shared version of remediation script, make RHEL-6 & RHEL-7 links to
  appropriate places

Fixes #319.

Testing report:
--
Tested both (the scan & remediation) at both of RHEL-6 & RHEL-7 products. Works as expected.

Please review.

Thank you, Jan.