Fixes our own, and upstream's, issues with the stricter Java 8 JavaDoc
linter.
Also removes the destroystokyo-release maven repository. I'm not sure
why I added it originally, but it's unnecessary now.
Also add "commands" to Tab Completion
Note: This required a signature change to Bukkit#reloadCommandAliases() so that it returns a boolean based on if the command aliases reloaded or not.