Set DNS ip and item-name automatically.

[slothbear]

assumptions:

• wither status already knows the IP address: droplet.public_ip
• The item number for this week is one more than last week: (new-ish) config var BOOT_RESTORE_WEEK

snags:

• The IP address is not assigned until the droplet starts, perhaps about 1 minute after the boot command.

IP

Since the IP isn't available immediately, just wait for it. When wither receives the phone_home at /cloud/booted/:instance_id, issue the DNS command (or equivalent).

possible sources of item yaml:

• (best so far) The Offical Minecraft Wiki list of [pre-flattened ids]. (https://minecraft.gamepedia.com/Java_Edition_data_value/Pre-flattening#Item_IDs). The items are separated into groups of 16, but a quick look at the structure makes me think it will be easy to scrape.
• ask somewhere (wiki? forum?) where to find the best YAML or CSV or other structured source.
• https://gist.github.com/hice3000/5868329 (8 years old)
• scrape the id list we already use? This table is messy. Each character in the item name is separated by a blank span. what? I guess the letters could be rejoined.