Update net class: add composition method

tenet/febTransduction/net/atom_property_net.py

tenet/febTransduction/net/class_net.py

tenet/febTransduction/net/composite_class_net.py

tenet/febTransduction/net/composite_property_net.py

tenet/febTransduction/net/individual_net.py

tenet/febTransduction/net/net.py

tenet/febTransduction/net/phenomena_net.py

tenet/febTransduction/net/property_net.py

tenet/febTransduction/net/restriction_net.py

tenet/febTransduction/net/value_net.py

tests/test_rule.py

tests/test_scheme.py

tests/test_semantic_net_1.py

tests/test_semantic_net_2.py

tests/test_semantic_net_3.py