Fixes#311.
* tests/python/ipnbdoctest.py: Adjust to process the new format,
with a lot of inspiration from Vcsn's copy of this file.
* tests/python/_altscc.ipynb, tests/python/_aux.ipynb,
tests/python/acc_cond.ipynb, tests/python/accparse.ipynb,
tests/python/alternation.ipynb, tests/python/atva16-fig2a.ipynb,
tests/python/atva16-fig2b.ipynb, tests/python/automata-io.ipynb,
tests/python/automata.ipynb, tests/python/decompose.ipynb,
tests/python/formulas.ipynb, tests/python/gen.ipynb,
tests/python/highlighting.ipynb, tests/python/ltsmin-dve.ipynb,
tests/python/ltsmin-pml.ipynb, tests/python/parity.ipynb,
tests/python/piperead.ipynb, tests/python/product.ipynb,
tests/python/randaut.ipynb, tests/python/randltl.ipynb,
tests/python/stutter-inv.ipynb, tests/python/testingaut.ipynb,
tests/python/word.ipynb: Upgrade to the new format.
* NEWS: Mention the change.
* spot/gen/automata.hh, spot/gen/automata.cc: Hide ks_cobuchi() behind
introduce aut_pattern(), as we have already done for the formulas.
* bin/genaut.cc: Simplify using this interface.
* python/spot/gen.i: Introduce aut_patterns().
* tests/python/gen.ipynb, tests/python/gen.py: Adjust.
This helps with autocompletion in IPython, and it will prevent us from
mixing LTL patterns with automata patterns (once we have more than one
automata generator).
* spot/gen/formulas.hh: Here.
* spot/gen/formulas.cc, bin/genltl.cc, tests/python/gen.ipynb,
tests/python/gen.py: Adjust.
* spot/gen/formulas.hh, spot/gen/formulas.cc (genltl): Rename as...
(ltl_pattern): This.
(ltl_pattern_max): New function.
* bin/genltl.cc: Adjust names, and simplify using ltl_pattern_max().
* python/spot/gen.i (ltl_patterns): New function.
* tests/python/gen.py: Test it.
* tests/python/gen.ipynb: New file to document the spot.gen package.
* tests/Makefile.am, doc/org/tut.org: Add gen.ipynb.