Issue 411 -- Follow-up example/cookbook fixes

[lsawade]

Description

Fixes:

• Fixed examples after station writing fix
• Fixed cookbooks
• Some of the plots had combined Z and X component plots, which are hard to read for more than 6 traces, so I split them up.
• For some examples, I added an "very" optional instruction on how to create a gif animation using ImageMagick
• Put example trace images into reference folder so that they aren't confused with the
• produced plots

Issue Number

Closes #411 (again)

Checklist

Please make sure to check developer documentation on specfem docs.

• I ran the code through pre-commit to check style
• My code passes all the integration tests
• I have added sufficient unittests to test my changes
• I have added/updated documentation for the changes I am proposing
• I have updated CMakeLists to ensure my code builds
• My code builds across all platforms