Fix command usage casing

[Jikoo]

• Fixed command usage containing capital letters
  • Mojang does not ignore case when executing commands as a part of their chat signing feature. Spigot does not ignore case when executing commands due to wanting to keep a minimal diff. Spigot always lowercases commands when registered, so GP suggesting uppercase letters in its command feedback is confusing for users.
• Removed unused permission declarations
• oh god the datastore had LF endings, there goes my readable diff to make sure I didn't miss anything after screwing up with a poorly-expressed replacement. Can't ignore whitespace until I make the PR. Looks okay, only sketchy-ish part is /claimslist because it uses the <command> placeholder twice and I'm not sure what replacement function Bukkit uses for that. Probably String#replace, probably fine.

Closes #1933