Spice Diode & Source fixups

As discussed:

• add ac=1 to VSIN
• add ac and vac keywords to VSIN
• hide sim properties for Device:D and Diode:* symbols
• change any 0mil-sized text to 50mil
• PWL I/V sources were raw spice elements, so I reconfigured them to be PWL I/V sources for nicer UX. The AM/FM sources are still raw spice elements because the spice model editor doesn't seem to support AM/FM modulated I/V sources.
• added dummy 1V DC model to B-source
• changed dependent source datasheets to point to ngspice docs
• some dependent source label adjustments

considered but decided against:

• remove 0 symbol from Simulation_SPICE because ngspice converts GND to 0 automatically