Re-implement plyr::eval.quoted, plyr::as.quoted

[MichaelChirico]

As with the others, it's not 100% clear there's a lot of value (besides maybe the new tests) in this PR at the moment. But since it's done, I'm sharing it anyway.

Written by Gemini.

This completes the series -- {plyr} is no longer required by package code.

It is still required by examples using plyr::.. So that would technically mean moving {plyr} to Suggests without further work (e.g. to re-implement . as a reshape2 export). Eschewing that for now.

reshape/man/cast.Rd

Lines 94 to 96 in 0337342

	library(plyr) # needed to access . function
	acast(aqm, variable ~ month, mean, subset = .(variable == "ozone"))
	acast(aqm, variable ~ month, mean, subset = .(month == 5))

If you're keen to adopt any subset of these changes, I can help by putting them in a jj stack that will facilitate merging without having to deal with so many merge conflicts among them. Let me know.