System for no longer actively listening to addresses

[Klakurka]

Here's my idea:

1. If it doesn't exist already, add a new column on the Address table called 'lastUsed'. This will track the last time the address came up in our system in some way. For example: adding it to a wallet, getting a ping about it from a paybutton out in the wild, etc.
2. Add a new Address.listening column. If we haven't heard from the address in a while (lastUsed gets too stale), then we will set listening=0 and stop listening to it on Chronik.
3. We add a new button in the UI to let users manually 'sync' buttons/addresses if they really want but people who would actually need this are people who aren't actually using paybutton so in theory it's not a must-have feature for v1. Clicking that button could buy them some more time, keeping the address as listening=1 for a while.