Gitorious Apocalypse: even more gitorious URLS

I believe these are the last few Gitorious URLs

Gitorious Apocalypse: remove all gitorious URLs

The Gitorious URLs will disappear in the next few hours. The canonical
hosting location of this project is now on copyleft.org. Specific
gitorious URLs are generally replaced with k.copyleft.org, which is
copyleft.org's self-hosted Kallithea instance.

Make attributions consistent.

Also, fix a few spurious characters.

Consolidate copyright notices into single place.

Historically, this project used (more-or-less) a file-by-file copyright
inventory. This commit ends that practice. The project now has a
single toplevel copyright inventory, stored exclusively in
comprehensive-gpl-guide.tex (so that it appears also in compiled
versions of the Guide as well).

The side-effect of this commit is that the parts may no longer be easily
publishable separably without (at least) the additional work of
copyright notice reconstruction. This may in particular create a
challenge for the FSF, who has historically selectively published
sections of this Guide as materials for its CLE classes.

However, without this change, this Guide will eventually suffer from the
inherent problems in maintaining file-by-file copyright inventory.
Circumstances simply dictate a single, top-level copyright and license
notice for the entire Guide.

In addition to consolidation of copyright notices, I've also herein
updated my historical copyright notices to properly credit me for my own
work done in 2003 through 2005.

I've also updated the license notice to reflect the changes made by the
previous commit and related issues.

Citations of third-party works in appendix only.

As alluded to in 2ea19b71d4a917babb29024f06acabfe73309f40 's commit
message on 2014-12-17 19:52:15 -0500, keeping any information on a
part-by-part basis is difficult and error-prone, since there exists no
reliable way to auto-generate such information accurately.

Therefore, citations to third-party works, in addition to remaining
fully documented in the commit log as they always have been, are now
placed in specifically one location in the body of the text itself: a
single appendix specifically designed for that purpose.

In this manner, contributors have no house-keeping work regarding
citations. Contributors need only list third party works and links in
one place: third-party-citations.tex.

Documentation in CONTRIBUTING.md for making contributions of third-party
works is left as a TODO.