Getting ready for PyPI

[yangdikun]

gpgLabs codes are clean. Next, tidy up the notebooks.

• Do we need to keep "Attenuation.ipynb" and "DataPlot.ipynb"?

• Naming convention. Proposal: MethodUseDescription.ipynb, e.g. MagLabFitProfile.ipynb, SeisTBLSeismogram.ipynb.

• Other typos, errors, corrections, adjustments. Need cross check.

• Everytime the sliders are dragged, the data files are downloaded again.

• Fix index page (there are two index.ipynb!)

• InducedMag2D: last section, obs and pre data maps not in the same size.

[thast]

@yangdikun : can we close this issue?