clean up repository

I don't like how the book is in a repetitive directory https://github.com/ioos/bio_data_guide/tree/main/bio-data-guide. It should be in something more self explanatory, like book/.

I like the https://github.com/ioos/bio_data_guide/tree/main/OBIS_data_tiers directory/readme, but I think it should be put into the book somewhere and that directory removed.

Ideally the structure should look like:

.github/workflows/
  [GH Action workflows]
book/
  [book raw contents]
datasets/
  [example datasets directories]
.gitignore
CITATION.cff
CONTRIBUTING.md
LICENSE
README.md
building-the-guide.md

probably can remove:

• https://github.com/ioos/bio_data_guide/blob/main/ESIP%20Data%20Citation%20Guidelines%20v2.pdf
• https://github.com/ioos/bio_data_guide/blob/main/bio_data_guide.Rproj