Accept dates in ExoneraTor in addition to timestamps

The current ExoneraTor implementations (web, Java, and Python) all require an IP address and a timestamp as input. However, people often only know a date and not a timestamp, so they'll have to guess a time like 12:00. Obviously, that's error-prone.

We should accept a date, too, and check whether the IP address was registered in the Tor network at any time of that day. The user can still refine the query by adding a time later on.

This task is assigned to Metrics Utilities, because it's probably easiest to change the Java or Python version in metrics-utils first. Once that's done, the web version in metrics-web should be updated, too.