Refactor Lumerical plugin to use PyLumerical #663

Is your feature request related to a problem? Please describe.
Ansys recently published https://github.com/ansys/pylumerical which appears to be the go-to method to access Lumerical with Python in the future. The API seems to be just lumapi but packaged nicely. Refactoring to use this instead of raw lumapi is likely worthwhile doing.