Enable XY -> YZ/XZ axis transformation

[pvnbhargava]

Lumerical unfortunately has a preferred axis, and only allows certain simulation types to be run along certain axes. For vertical grating couplers, the XY plane is not in alignment with the 2D FDTD simulation setup and must be rotated.

Initial approach

• Within PhotonicTemplateDB add support for a preferred plane XY, XZ, or YZ. By default, XY plane will be chosen.
• Add plane parameter to the lsf_export() methods of all the basic shapes so that they can internally choose which plane the code should be written to.

[pvnbhargava]

This turns out to be practically infeasible. It turns out that Lumerical makes hard assumptions that the vertices in all polygons represent those in the XY plane, and there is no way to change it around...

The "solution" is to just use 2.5D fdtd and live with the increase in simulation time for now