Add OP variables dump feature

[ra3xdh]

This feature was requested by @dwarning in discussion #761 It should be technically possible to dump the OP variables like @D1[cd] The following tasks should be done:

• The @ symbol is reserved for PlotVs emulation in Ngspice mode. It's need to resolve this conflict.
• Add a special parameter for every simulation like DumpOPVars=true/false
• Add a property like OPVars in the Component class