getting started documentation

[sbillinge]

Problem

no human written docs as yet

Proposed solution

Write the docs including a step by step getting started

[yucongalicechen]

Per discussion in #113: add examples/instructions for entering username and email in the config file.

[yucongalicechen]

From #153 and #151: explain in docs about what's going on in WAVELENGTH

[sbillinge]

@yucongalicechen where it makes sense we can reuse text from the paper. For sure, cite the paper in the package, but we can also reuse parts of the text where it makes sense.

[yucongalicechen]

(Just to keep notes about what to add in the docs besides the explanation for functions and use cases)

Write Utilities and Examples for:

• labpdfprocapp.py: include a step to step getting started, explain gui (update doc/tutorial for gooey #132, GUI widget only supports files, folders must be typed - needs docs clarification #148), explain the different muD options we have once we implemented that issue (currently muD is still a required argument and we don't support multiple muDs)
• functions.py: explain how we recommend to use even n instead of odd n to avoid sampling points on the circle,
• tools.py: update about wavelength