Split `{ppgames}` into separate packages

[trevorld]

• [x] Put setup generating functions in one package

  • Merge with {tradgames}?

• [x] Put plaintext diagram functions in one package

• [x] Put PPN functions in one package

• [x] Put solver(s) in one package

• [x] Put ruleset generators in one package

• [x] Write piecepackr::install_ppverse() that installs all libraries in this family

• [ ] In {ppgames} .onLoad() add new startup message advising users to switch to {ppverse} instead

• [ ] "archive" {ppgames}

[trevorld]

• {ppdf} is public now: https://github.com/piecepackr/ppdf/

[trevorld]

• {ppcli} is public now: https://github.com/piecepackr/ppcli

[trevorld]

• {ppn} is public now: https://github.com/piecepackr/ppn

[trevorld]

• {ppgamer} is public now: https://github.com/piecepackr/ppgamer

[trevorld]

• {pprules} is public now: https://github.com/piecepackr/pprules

[trevorld]

Instead of trying to re-integrate the new split off packages into {ppgames} I'll instead plan on:

1. Write new {ppverse} collection package that installs/loads all {ppgames} split-off-packages and {piecepackr} and perhaps {piecenikr}
2. In {ppgames} .onLoad() put in a new package startup message advising users that {ppgames} is superseded and switch to {ppverse}
3. On Github "archive" {ppgames}

So {ppgames} should still be installable and usable with the only change being a new start-up message suggesting that they switch to the new packages and we'll be closing new issues in its Github page.