Resolves #78

This removes all of the notebooks and code, except for:

• The 01_introduction notebook, which now only contains overview information about (pre)icebridge/icesat/icesat2 altimetry data. It does not provide any code for searching/accessing/harmonizing data.
• The corrections notebook. This remains unchanged, describing to users the importance of harmonizing the CRS of data across missions, and using a synthesized dataset as an example
  • We will address adding a real-world example to the corrections notebook in Add real-world example of dataset ITRF transformation #76