Cleaned up notebooks based on feedback from pilot

See merge request !2

# Conflicts:
#   python-data-3-numpy.ipynb
#   python-data-5-pandas.ipynb

slimmmed down all of the material
split the regex part from the pandas notebook into its own seperate notebook

Updating local copy of devel to include new plotting notebook.

Plotting Notebook

See merge request !1

added missing datasets
made some new extra exercises

This reverts commit 72f7777a.

In python-data-0.ipynb: fixed minor typos.

In python-data-1-recap.ipynb: fixed minor typos and errors, separated
checking code blocks.

In python-data-2-words.ipynb: fixed typos, updated to include
filepaths and changed function arg. names to avoid clash with global
variable "filename".

In python-data-3-numpy.ipynb: fixed typos, and added extra
explanations in exercises at end of workbook on plotting/distance.