More detailed TA activity statistics

Summary

It would be great if there would be an overview of activity per TA per lab. Currently we have a magic "active TA's in the last hour" number, but I would like a bit more. Such as a list of:

• TA name
• Timestamp of first accepted request in the lab
• Timestamp of la(te)st accepted request in the lab
• Total number of requests handled in this lab
• Average time spent per request in this lab

Reasoning

Currently there is no easy way to check whether all TAs that were scheduled are actually active during a lab, outside of a total number and manually checking requests per TA or something. It would be nice if we would be able to see in an overview (table) which TAs are active together with some statistics.