Simplify & Update .gitignore to match IDEA
Update license year, Improve JavaDocs & comments, Reformat source
Update pom with better style, Elimiinate the need to manually change the project version in plugin.yml
Replace some explicit object arrays with varargs

How did that sneak into there?
Fix various code style issues, Improve console logging
Always clone ItemStacks to prevent issues
Make help more flexible in MessageBundles
#UX: Default amount to 1 if not specified
Print help when an unknown Material is specified - Might be that the users wanted to execute a sub command that doesn't exist