Reflection and refraction of plane waves

[sgkang]

This is a missing piece, and some materials are scattered (e.g. MT layered solution) Structure will follow WH Section 3. Reflection and refraction of plane waves, but summarize gist of the context.

• [x] Snell's law
• [x] Fresnel equations
• [ ] Wave impedance and impedance at plane interface
• [x] Total reflection and Brewster angle

Note:

• Should merge response of layered earth to a plane wave (Layered earth impedance)
• Thought process: Bukpronong (AEM) -> Fields from inductive source (layered earth) -> Reflection and refraction

[sgkang]

See Pull request of #351 for three items done, but third item needs to be done. @thast is already done some work about this, but can you move current wave impedance stuff in MT to fundamentals? and make it more solid?