merged w/ develop and updated a whole lot of things

README.md

b_asic/GUI/drag_button.py

b_asic/GUI/main_window.py

b_asic/GUI/properties_window.py

b_asic/GUI/simulate_sfg_window.py

b_asic/__init__.py

b_asic/core_operations.py

b_asic/operation.py

b_asic/port.py

b_asic/save_load_structure.py

b_asic/schema.py

b_asic/signal_flow_graph.py

b_asic/special_operations.py

test/fixtures/signal_flow_graph.py

test/test_abstract_operation.py

test/test_operation.py

test/test_schema.py

test/test_sfg.py