Formatting, spacing, final modifiers, and a few code fixes

[Draycia]

• Use append instead of string concatenation in StringBuilder
• Remove unnecessary casts in the PlaceholderAPI class
• Add final modifiers to some fields
• Ensure line width doesn't exceed a certain amount
• Add spacing mostly where appropriate

[darbyjack]

Thanks for this. I'll look over it with clip in the coming days and hopefully, this will be pulled into the next update!

[extendedclip]

Will follow up with this pr when I get home from vacation.