Deprecate packages

This is my attempt to kill off some packages, a test of the idea of using a max Julia version as a safe way of doing it that should break existing installs (hopefully).

* Package isn't deleted
* Listing generators like my one won't list them
* Can override the version limit if you want to install (to e.g. recreate results)

Related discussion here: https://github.com/JuliaLang/julia/pull/6669

I have partially re-implemented https://github.com/JuliaLang/METADATA.jl/pull/732, as well as deprecate Monads.jl (https://github.com/pao/Monads.jl/issues/4) and Trie.jl (https://github.com/JuliaLang/METADATA.jl/pull/820)

Should the Julia max versions be `0.3` or `0.3-`?