Refined Security Groups terminology article

Improved the description; added more xrefs to the
community docs

Change-Id: I5fb8126f5bb07da58dd82973b5f2cdb71cd3238e
Merge "Refined Security Groups terminology article"
Fixes and cleanups for missing lables

* Moved release notes to other pdf files. Building them as
  a separate job is not only pointless but also doesn't
  allow referencing other chapters with :ref tag from the
  release notes.

* Cleaned some broken references and labels.

Change-Id: I8029b6e165450214c01113818a29d9102a53cd30
Merge "Fixes and cleanups for missing lables"
run `aspell' against our documentation

Change-Id: I1cb7727da0f87bcf4ed689c4bcc82ae94a4ae7fa
correct statement about CPU utilization and GRE

- according to discussion on mailing list
  (https://lists.launchpad.net/fuel-dev/msg01084.html) usage of GRE
  protocol *increases* CPU utilization on endpoint nodes, our
  documentation states the opposite, which is wrong.

Change-Id: Ia2f835a68c7ecbf812fb916a143d50423f126d40
Add and remove addshadow class on move hover on TOC

Change-Id: I94a73a83764293081e2af8cfc0b22f58116c7933