Handle subcircuit "uplifting"

[aidangoettsch]

There's some commented out logic that attempts to pull the contents of subcircuits up a level, so, for example, small digital circuits include their analog components. Currently, the command line argument -d/--depth controls the depth to which the program should pull out nested subcircuits.

The main challenge ends up being correlating the index of components (which is how connections identify what they are connected to) between the lower level subcircuit and the new larger circuit, as well as connecting components that were connected to pins/inputs.

To be useful, this likely requires #1.