big help upgrades

- short descriptions for command list
  - argument descriptions
  - render argument list on detailed help page

commands/message/core/undo.js

@@ -7,6 +7,7 @@ module.exports = {
   label: 'amount',
   metadata: {
     description: 'Remove recent command responses from chat.',
+    description_short: 'Undo last command',
     examples: ['undo 5'],
     category: 'core',
     usage: 'undo [<amount (1-5)>]'