modernize the logo

* doc/org/spot2.svg: New file.
* doc/Makefile.am: Distribute it.
* doc/org/.gitignore: Adjust.
* doc/org/setup.org: Display it.
* doc/org/autcross.org, doc/org/autfilt.org, doc/org/citing.org,
doc/org/compile.org, doc/org/concepts.org, doc/org/csv.org,
doc/org/dstar2tgba.org, doc/org/genaut.org, doc/org/genltl.org,
doc/org/hierarchy.org, doc/org/hoa.org, doc/org/index.org,
doc/org/install.org, doc/org/ioltl.org, doc/org/ltl2tgba.org,
doc/org/ltl2tgta.org, doc/org/ltlcross.org, doc/org/ltldo.org,
doc/org/ltlfilt.org, doc/org/ltlgrind.org, doc/org/ltlsynt.org,
doc/org/oaut.org, doc/org/randaut.org, doc/org/randltl.org,
doc/org/satmin.org, doc/org/tools.org, doc/org/tut.org,
doc/org/tut01.org, doc/org/tut02.org, doc/org/tut03.org,
doc/org/tut04.org, doc/org/tut10.org, doc/org/tut11.org,
doc/org/tut20.org, doc/org/tut21.org, doc/org/tut22.org,
doc/org/tut23.org, doc/org/tut24.org, doc/org/tut30.org,
doc/org/tut31.org, doc/org/tut50.org, doc/org/tut51.org,
doc/org/upgrade2.org: Include setup.org instead of declaring it as
SETUPFILE.
* doc/org/spot.css: Add entries for the logo.
* python/ajax/trans.html: Use the new logo.
* python/ajax/logos/mail.png, python/ajax/logos/spot64s.png: Delete.
* python/ajax/Makefile.am: Adjust.

doc/org/setup.org

@@ -6,3 +6,6 @@
 #+MACRO: LASTTARBALL [[http://www.lrde.epita.fr/dload/spot/spot-2.5.3.tar.gz][=spot-2.5.3.tar.gz=]]
 #+MACRO: LASTNEWS [[https://gitlab.lrde.epita.fr/spot/spot/blob/spot-2-5-3/NEWS][summary of the changes]]
 #+MACRO: LASTDATE 2018-04-20
+
+#+ATTR_HTML: :id spotlogo
+[[file:spot2.svg]]