compel: Drop unneeded FIXME and add new one

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
docs: Update compel

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
docs: Add compel-plugins

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>