Big PR to bring things up to date with work from another project

[mbrousil]

Sorry this is a big PR! Honestly though there's not a ton new compared with what's been going on in the Light Partitioning project where a lot of this was being cooked up. This is mostly to just port over a few months' work there into the main AQ2 world. So it should largely be copy/pasting code of code that you've already seen.

Major updates:

• Add in the basics for pulling temp, N, & P
• Manually broke up the process of downloading by parameter to help w/ memory usage
• Add a "strict" version of cleaning processes
• Created a basic automated bookdown process for documenting harmonization
• Some other changes to how datasets are exported/read/etc. to help w/ memory usage

I just need a high-level review: do things look right, not a line-by-line read.

[mishafredmeyer]

This looks great to me! If you are satisfied with things, go ahead and merge with the main branch!