Functions and macros facilitating writing, management and updating of R documentation

Functions for manipulation of R documentation objects, including functions for updating existing Rd documentation for functions, methods and classes; Rd macros for citations and import of references from BibTeX files for use in Rd files and roxygen2 comments; Rd macros for evaluating and inserting snippets of R code and the results of its evaluation or creating graphics on the fly during package building; and many functions for manipulation of references and Rd files.