Arranging plots: slide edits

[kaijagahm]

Edited text on slides, cleaned up some formatting, removed section numbering, and split up several slides into smaller slides to eliminate scrolling.

Deliberately included the code to create the initial 4 plots to establish what we're working with.

Added comparison of tag_level = "new" vs. tag_level = "keep" because I didn't understand it (and maybe still don't?)

[jonthegeek]

Thanks! The chapter headers (# level) should be numbered, so don't add {-} on those. The numbering was off, though, because chapter 1 was marked as unnumbered (making everything else also wrong). Hopefully this will fix it. Thanks again!