Improve measurement of spent time for tasks/annotations

[philippotto]

Time spent by annotators is measured automatically by wk. TimeSpans are stored in postgres describing the work.

When a user sends an annotation update request to the Tracingstore, it sends a summary on to the webknossos server (remoteWebKnossosClient.reportTracingUpdates)/ WKRemoteTracingStoreController.handleTracingUpdateReport).

Some users have asked that move-only updates, where no segments/nodes were modified should not be counted for the time tracking. The report already contains a significantChangesCount.

An application.conf parameter should be added to disable timetracking for updates with significantChangesCount==0.

Note for testing this: currently, only timespans of tasks are available in the UI. You can still use postgres to inspect stored timespans for explorative annotations. Compare #7524

More sophisticated ideas (that we decided against for the moment) include

• Setting per project instead of instance-wide application.conf setting
• For each update, use only the timestamps that stem from “significant changes”
• Also include timestamps for move-only events except if move-only occurs for more than x seconds

Context

Internal discussion.