doc: re-wrap design-oob to 72 chars
doc: re-wrap design-oob to 72 chars

I started with just adding some :term:`SoW` and similar to design-oob,
but then I realised this was 80-chars wrapped, not 72-chars. So I went
and re-wrapped most of it, plus adding the glossary references.

Signed-off-by: Iustin Pop <acf83a5274f31a43af6b914614365999469c1a31@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

bitemyapp/ganeti,leshchevds/ganeti,apyrgio/ganeti,yiannist/ganeti,dimara/ganeti,bitemyapp/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,grnet/snf-ganeti,mbakke/ganeti,onponomarev/ganeti,andir/ganeti,leshchevds/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,ganeti/ganeti,ganeti/ganeti,leshchevds/ganeti,yiannist/ganeti,ganeti/ganeti,andir/ganeti,dimara/ganeti,apyrgio/ganeti,ganeti-github-testing/ganeti-test-1,onponomarev/ganeti,mbakke/ganeti,grnet/snf-ganeti,andir/ganeti,apyrgio/snf-ganeti