Improve ARTS surface properties integration in Disort and RT4

[olemke]

• Implement consistent treatment of surface between RT4 and Disort.
• Possibly utilize BRDF support offered by C Disort to implement non-Lambertian surfaces.

Can be started after PR #80 is merged.

[erikssonpatrick]

Probably done for RT4, and I have given up on DISORT for now. But status of code needs to be revised..

[dhjx1996]

Probably done for RT4, and I have given up on DISORT for now. But status of code needs to be revised..

How is DISORT going?