Library updated using the fast fitter and inclusion of Palik materials

[e-g-melo]

Issues #1021 and #1022.

• A lot of materials were updated and improved using the new fast fitter.
• Inclusion of Palik materials: Si, SiO2, GaAs, Ge, InP, and InAs.
• The Palik materials were split into lossless and lossy wavelength ranges to improve the fits.

[tomflexcompute]

Thanks @e-g-melo . I randomly tested a few and they all look good. The inclusions of palik Si and SiO2 are going to be very welcomed by users in the PIC industry!

[tomflexcompute]

By the way could you add it to the change log? Something like "improved fitting for materials in the material library. Added a number of common semiconductor materials such as Si, GaAs, and InP from Palik to the material library."

Also I see a conflict which is due to another PR today that added the reference for graphene on material_refernece.py. It should be straightforward to resolve.

[weiliangjin2021]

Looks quite good. One general comment is that if the material is based on an analytical model provided in the paper, we should use the poles referred directly from the analytical modal. This is usually indicated if the variant name has the word "Drude", "Lorentz", "Sellmeier", etc. If you find the pole is imaginary, they are likely based on Sellmeier model.

[weiliangjin2021]

Here is what I would suggest:

• A list of materials to remain in its original form
  • AlAs_FernOnton1971: Sellmeier, eps_inf in its original form is likely to be off
  • GaAs_Skauli2003: Sellmeier
  • Ge_Icenogle1976: Sellmeier, eps_inf in its original form is likely to be off
  • InP_Pettit1965: Sellmeier, eps_inf in its original form is likely to be off
  • Si3N4_Luke2015: Sellmeier
  • Si3N4_Philipp1973: Sellmeier
  • Y2O3-Nigara1968: Sellmeier
  • YAG_Zelmon1998: Sellmeier
  • cSi_SalzbergVilla1957: Sellmeier
  • cSi_Li1993_293K: Sellmeier
  • All variants that contains "PMLStable" keyword

[e-g-melo]

Thanks Weiliang! I've changed all these materials to their original forms.

[weiliangjin2021]

Green light from me to merge once the commits are squashed.