dot: make "a" the default
Fixes #319.
* spot/twaalgos/dot.cc: Enable "a" by default.
* bin/common_aoutput.cc, NEWS: Document it.
* doc/org/autfilt.org, doc/org/concepts.org, doc/org/dstar2tgba.org,
doc/org/hierarchy.org, doc/org/ltl2tgba.org, doc/org/oaut.org,
doc/org/randaut.org, doc/org/satmin.org, doc/org/tut23.org,
doc/org/tut24.org, doc/org/tut30.org, doc/org/tut31.org: Adjust or
simplify the documentation.
* tests/core/det.test, tests/core/dstar.test, tests/core/monitor.test,
tests/core/neverclaimread.test, tests/core/readsave.test,
tests/core/tgbagraph.test, tests/core/wdba.test,
tests/python/_autparserr.ipynb, tests/python/automata-io.ipynb,
tests/python/automata.ipynb, tests/python/highlighting.ipynb
tests/python/ltsmin-dve.ipynb, tests/python/ltsmin-pml.ipynb,
tests/python/product.ipynb, tests/python/testingaut.ipynb,
tests/python/word.ipynb: Adjust test cases.
2a308182db