Notable changes:

• Lots of fields have been made final, especially in enums to prevent anyone from modifing them from another plugin (and therefore creating untracable bugs)
• Many string concatenations in stringbuilder calls have been split into the correct append calls
• In CommandFilter, an ArrayList masquerading as a map has been replaced with an actual map
• Replaced another string equals chain with switch
• Lots of unnecessary modifiers, especially in interfaces, have been removed
• In AsyncListenerHandler a HashSet of Integer was replaced with an IntSet