Persistent dynamodb garbage collector

[bbangert]

Create a script that runs persistently on a machine to sweep old/dead data out of DynamoDB.

This script should be runnable by cron, save its place (using dynamodb last-key/start-key for table scans), and watch the dynamodb capacity usage to avoid using up available capacity.

Rough outline of run logic:

• Get prior start location in router table (perhaps saving the location each run in Dynamodb as well)
• Router Table scan for N UAID's
• If the user hasn't connected in M days, check storage/message table and clear old data
• If the user hasn't connected in Z days, clear out user/storage/message entirely
• Save last-key from router table scan

[bbangert]

Dumping in favor of table rotation.