Update kits and item spawning docs

[mdcfe]

We already have the BannerMeta page, but the other Essentials wiki pages are outdated and don't cover everything in EssentialsX.

Kits

Can adapt from Essentials wiki; the main differences are:

• Kits are now in kits.yml
• EssX adds /createkit which creates mostly-accurate kits (note these aren't perfect), and /delkit
• You can use commands in kits in EssentialsX

Item spawning

Again, we can adapt from the Item Meta and Command Reference/Spawning pages. Main differences:

• Item IDs don't work on 1.13 or above
  • "Damage values" that were used for alternative versions of the block won't work any more because these were flattened
  • Durability values for a tool's actual durability still exist
• Some item meta might have changed over the years
  • Potions in 1.9-1.12 work somewhat differently to 1.8 and before, but who knows what exactly
  • Potions in 1.13+ are distinct items in the item database
• You can now use the | character in lore by escaping it with a backslash