Add citation generator

[NateMietk]

Request the the Data Standards Technical Working group.

• Add text in neonUtilities package after user kicks off stackByTable that is a disclaimer to cite the data, and how to properly cite the data.

• Create a function within all data downloading functions to collect information on the data used to populate a bib text file that will allow users to easily add to a citation manager.

As a starting point: https://github.com/ropensci/popler/blob/master/R/popler_citation.R