LU-883 build: allow blank after signoff, email fix

LU-883 build: allow blank after signoff, email fix

Allow blank lines after the signoff section, since there will usually
be a blank line between the signoff and the checkpatch.pl output.

Improve the EMAILPAT regex to detect bad email addresses that do not
have a full name (at least 2 parts) and a full domain (also with
at least 2 parts).

Allow a generic "{Organization}-bug-id:" line in the signoff section
to allow linking the patch commit into arbitrary bug databases for
ease of tracking patches.

Add test cases for all of these changes.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Iaf14f6c985d3dd4837064d29071bd9acd8031d67
Reviewed-on: http://review.whamcloud.com/1867
Reviewed-by: <bruce.korb@gmail.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Bobi Jam <bobijam@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>