Aggregator & delete user

Now using the Aggregator from Pypi instead of the copied code. Also has the 'permanently delete user' admin option. Note that this changes requirements.txt and thus a fresh docker container build.

What's Changed

• Added fix schema functionality by @tmtabor in #350
• Issue 351 by @liefeld in #355
• Attempt to make shutdown more reliable and prevent the case where dja… by @liefeld in #354
• New aggregator version by @jluebeck in #356

Full Changelog: v2.9.1_060525...v2.10.0_071825