Circuit conversion to STG creates additional signals for outputs

[Danil Sokolov]

Circuit conversion to STG creates separate signals for the driver gate and for the primary output itself. Instead only a signal for the gate output should be created, but named more cleverly:

 - If a gate is connected to a single primary output, then the signal associated to the gate output contact should take the name of the output port and its type should be OUTPUT.

- Otherwise, if a gate does not drive an output port, then the signal name should be the name of the gate itself and the type INTERNAL.

- Otherwise, if a gate has several output contacts, then they should be named <gate_name>_<contact_name>.