sat_minimize: improve logs and document Python bindings

* spot/priv/satcommon.cc, spot/priv/satcommon.hh: Make it possible to
set the log file without setting the environment variable.  Adjust
print_log to take the input state and print it as a new column.
* spot/twaalgos/dtbasat.cc, spot/twaalgos/dtwasat.cc: Adjust all
calls to print_log.  Fix log output for incremental approaches.
Prefer purge_unreachable_states() over stats_reachable().  Do
not call scc_filter() on colored automata.
* spot/twaalgos/dtwasat.hh: Document the new "log" option.
* NEWS: Mention the changes.
* tests/python/satmin.ipynb: New file.
* tests/Makefile.am: Add it.
* doc/org/satmin.org, doc/org/tut.org: Link to it.
* doc/org/satmin.org, bin/man/spot-x.x: Adjust description
of CSV files.
* bench/dtgbasat/gen.py, bench/dtgbasat/tabl.pl,
bench/dtgbasat/tabl1.pl, bench/dtgbasat/tabl2.pl,
bench/dtgbasat/tabl3.pl, bench/dtgbasat/tabl4.pl: Adjust for
the new column.
* spot/misc/satsolver.cc, spot/misc/satsolver.hh (stats): Make it
const.
* python/spot/__init__.py (sat_minimize): Add display_log and
return_log options.
* tests/python/ipnbdoctest.py: Adjust to not compare SAT-minimization
logs as they contain timings.

NEWS

@@ -40,6 +40,15 @@ New in spot 2.5.2.dev (not yet released)
     example, the translation of GF(a <-> XXb) to transition-based
     Büchi went from 9 to 5 states using that construction.
 
+  - Slightly improved log output for the SAT-based minimization
+    functions.  The CSV log files now include an additional column
+    with the size of the reference automaton, and they now have a
+    header line.  These log files give more details and are more
+    accurate in the case of incremental SAT-solving.  The python
+    bindings for sat_minimize() now have a display_log and return_log
+    options; there are demonstrated on the new
+    https://spot.lrde.epita.fr/ipynb/satmin.html page.
+
   Bugs fixed:
 
   - "autfilt --cobuchi --small/--det" would turn a transition-based