Netlist: Added large signal diode model and fixed a number of bugs. 
Things like

    // astable NAND Multivibrator
    NETDEV_R(R1, 1000)
    NETDEV_C(C1, 1e-6)
    TTL_7400_NAND(n1,R1.1,R1.1)
    TTL_7400_NAND(n2,R1.2,R1.2)
    NET_C(n1.Q, R1.2)
    NET_C(n2.Q, C1.1)
    NET_C(C1.2, R1.1)

now work, though too many proxy devices are currently needed.