Rename `Analysis` to `Question`

[cortadocodes]

Decide whether we want to rename Analysis to Question in the next release with a breaking change.

[cortadocodes]

Following some discussion, we've decided not to do this as an analysis may in future also be used for non-terminating processes that don't fit the question-answer model we're currently using (e.g. a monitoring service that sends monitor messages to whichever parents call it).

[cortadocodes]

Two years later and @thclark and I note that the above scenario hasn't played out - reopening for further consideration.