New R6 classes `Labels` and `Taxa`

[jasonratcliff]

Add classes to format specimen voucher labels for typesetting to PDF.

• Taxa parses taxonomic terms to bold and italicize generic, (infra)specific terms

  • Include authorship from latest descriptions

• Labels formats records into LaTeX environments for multi-column specimen labels

  • Additional DWC terms are utilized for associatedTaxa and occurrenceRemarks
  • Private methods defined:
  • $coordinates() to label geospatial coordinates relative to CRS axis
  • $elevation_ft() to standardize elevation from m to ft.
  • $associations() to separate associated taxonomic occurences
  • $open() / $close() to handle environment even and odd record formatting
  • $preamble() with LaTeX shared document formatting
  • $label() for individual record typesetting