Implement .getCoulombForceAt(x, y, testCharge) method in MD2D engine

[#48204939]
Provide 'electricForceField' as MD2D model output

[#48204939]

Form of this output is:
[
  {x: <val>, y: <val>, fx: <val>, fy: <val>},
  {x: <val>, y: <val>, fx: <val>, fy: <val>},
  ...
];