Resolve "Load/Save SFG to file"

I added the ability to read from a .py file by executing it's lines and adding them to a given namespace, this allows the user to create scripts to read from without needing to explicitly import the script themselves somewhere in the source. I kept the previous load and save since I think they may have a purpose as well. Closes #66 (closed)

b_asic/__init__.py

@@ -12,3 +12,4 @@ from b_asic.signal_flow_graph import *
 from b_asic.signal import *
 from b_asic.simulation import *
 from b_asic.special_operations import *
+from b_asic.utils import *
\ No newline at end of file