new method: Region.diff
rm Polytope methods __add__, __sub__, __and__

because they are not closed: they return a Region instead of Polytope in certain cases.
Reflect changes where polytope.polytope is used.
update synth.is_realizable to new synthesize signature

which accepts env and ignore_env_init
make robot_controlled_switching_test a test
mv switching test from developer examples to test, rm robot from filenames
update png filenames
TEST: Use basic test fixture for jtlvint
TEST: Refactor (the name "aut" has lost favor); delete unused variable
TEST: Single test for case jtlvint.synthesize() given unrealizable
DOC: Correct described return value of jtlvint.synthesize()

What is worse than no documentation?  Incorrect documentation.
bugfix: remove duplicate next operators

introduced in 597ea881f2d70dbc13f825d6ab6197e2bdd15c63
Merge branch 'logging'