Adding python functions to mirror the functionalities found in src/bin

* wrap/python/spot.i: Rename to...
* wrap/python/spot_impl.i: ...this, and import spot_impl from spot.py so
that it is not needed to recompile everything when modifying python
code.
* wrap/python/spot.py: Adding python functions to mirror the
functionalities found in src/bin.
* src/bin/common_r.cc: Move simplification level...
* src/ltlvisit/simplify.hh: ... here as a constructor of
ltl_simplifier_options, to make it available in wrap/python.
* src/bin/ltlfilt.cc: Set simplification level using the new
ltl_simplifier_options constructor.
* src/bin/randltl.cc: Move most of the code...
* src/ltlvisit/randomltl.cc, src/ltlvisit/randomltl.hh: ... here, as a
class named randltlgenerator.
* wrap/python/tests/bddnqueen.py, wrap/python/tests/minato.py: Avoid
calling bdd_init twice by moving 'import spot' after bdd initialization.
* wrap/python/Makefile.am: Rename spot to spot_impl
* wrap/python/tests/Makefile.am: Add ipnbdoctest.py.
* wrap/python/.gitignore: Rename spot.py to spot_impl.py
* src/ltlvisit/tostring.cc: \ttrue and \ffalse should be \top and \bot.
* wrap/python/tests/ipnbdoctest.py: Run code cells of a python notebook
and compare the output to the actual content of the notebook.
* wrap/python/tests/randltl.ipynb: Document and test randltl.
* wrap/python/tests/run.in: Call ipnbdoctest.py to run ipython
notebooks.

src/ltlvisit/tostring.cc

@@ -273,8 +273,8 @@ namespace spot
       };
 
       const char* sclatex_kw[] = {
-	"\\ffalse",
-	"\\ttrue",
+	"\\bot",
+	"\\top",
 	"\\varepsilon",
 	" \\oplus ",
 	" \\rightarrow ",