Code fixing Spice device names (prefixing reference with a character
corresponding to the assigned device model type) that was duplicated in
a few places has been moved to a function (NETLIST_EXPORTER_PSPICE::GetSpiceDevice()).
netlist generation: remove option "replace IC and U ref by X" (broken option).
All component refs are now prefixed by the Spice_Primitive field value.
Therefore the netlist used by Kicad ngsipce simulator and the spice netlist generated from dialog are the same.
(note: like previously, forbidden chars like ( and ) are replaced by _ in netnames)
This commit creates more issues than resolves. It could happen that
there are components with different reference types (e.g. U1 and IC1)
that would be later converted to X1, causing a conflict.