Automate the listing of deprecated functions

[c5sire]

Goal: to only add deprecation information to the outdated function. Have a way to automatically extract that information and compile it into a user visible list.

For an option see: https://www.r-bloggers.com/r-deprecate-functions-with-roxygen2/

Created the 'deprecate' branch to work on it. Implemented for two functions. However, it appears roxygen2 somehow inserts non-ASCII code in the generaed Rd files for the functions on my Windows machines, which then causes warnings in the R CMD check.

Stopped for the moment. Until further investigation.