solr: add startup plist

Added a plist startup like was previously done in
[solr36](https://github.com/Homebrew/homebrew-versions/commit/4fa8b9b3c8f37667f1d993a53a6b9da383d87179)
at Homebrew/homebrew-versions#366.

Defaults to running Solr on port 8984 so it can run in parallel with
solr36 which runs on port 8983.
solr: add 4.9.0 bottle.