AUI.Boot disk space (housekeeping)

We have a build machine with persisting AUI.Boot cache (`~/.aui`) which repeatedly runs out of disk space because of AUI's cache. Because we often update our dependencies' versions, the older ones are still kept, leading to the disk problem.

AUI.Boot should have at least an option to somehow figure out the problem.

We can add `rm -rf ~/.aui` to cron but it would break the running builds.

The issue names AUI.Boot and its ~/.aui cache, but no source file, test, or entry point. Start by locating the cache-management code and tracing how dependency versions are retained; done should include a clearly defined way to identify or clean obsolete cache data without disrupting running builds.

Written by the indexing model from the issue text.