Documentation: convert tutorials to man pages
This patch renames the following documents and at the same time converts
them to the man page format:
cvs-migration.txt -> gitcvs-migration.txt
tutorial.txt -> gittutorial.txt
tutorial-2.txt -> gittutorial-2.txt
These new man pages are put in section 7, and other documents that reference
the above ones are change accordingly.
[jc: with help from Nanako to clean things up]
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>