ATL08 icepyx intro tutorial example

[JessicaS11]

I put together a quick intro tutorial for a demo at the ICESat-2 Applied Users Working Group Quarterly call (12 May 2021). I've added it as an example, since I used ATL08 and we often get requests for examples showing non-ice datasets.

I also removed some old dev/draft notebooks that were still hanging around.

[codecov-commenter]

Codecov Report

Merging #202 (2773102) into development (f2c6a5f) will not change coverage.
The diff coverage is n/a.

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  Coverage        55.63%   55.63%           
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  Files               20       20           
  Lines             1517     1517           
  Branches           316      316           
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  Hits               844      844           
  Misses             616      616           
  Partials            57       57           

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[github-actions]

👈 Launch a binder notebook on this branch for commit ada4d62

I will automatically update this comment whenever this PR is modified

👈 Launch a binder notebook on this branch for commit 7bd9ce9