Better mesh refinement along injection axis of lumped ports

[dmarek-flex]

The present choice for mesh refinement at lumped ports is suitable for the transverse dimensions of the port, but can lead to over refinement along the normal axis. What we really need is to ensure that a grid cell boundary is introduced exactly at the position of the port, as well as a reasonable choice for the grid cell size.

We need to determine what kind of grid cell size is appropriate for the normal axis of ports.