Replace << connect operator with <<= and overload shift

b_asic/architecture.py

b_asic/operation.py

b_asic/port.py

b_asic/sfg_generators.py

docs_sphinx/index.rst

examples/connectmultiplesfgs.py

examples/firstorderiirfilter.py

examples/folding_example_with_architecture.py

examples/lwdfallpass.py

examples/schedulingexample.py

examples/thirdorderblwdf.py

test/fixtures/signal_flow_graph.py

test/test_operation.py

test/test_schedule.py

test/test_sfg.py