Analytics should report back info / errors / warnings to the user

[tomchop]

Currently, analytics tasks can only report errors (exceptions) that get caught by the runner. It would be good if they could also report success or warning messages: a very simple structure with a datetime and a message field.

This would be particularly useful for oneshot analytics that run "too fast" and can get quite confusing to the user when they stay green in the UI.

[itsmvd]

I can take a look at this