Netlist:
- Working Ebers Moll model. That's a significant step ahead.
- Simple 2x2|RHS SPICE stamps now supported by two terminal devices.
  This was implicitly contained in the design, but set_mat now shows how
  a two-terminal device fits into a SPICE approach.
- Introduced direct solvers for net groups with 1 or 2 nets.
- Introduced specialized solvers for N=1,2,3,4,5 by using templates.
- nice performance increase for BJTs