Bulk delete of Tasks #1088

It is possible to conveniently delete a single Task from the task list. It is working well.

However, we know from real life use cases that people tend to create multiple tasks at the same time. While it is fair to assume that the admins will have incorporated the auto-delete mechanism, it is potentially not a very frugal approach and it can potentially pollute the list of Tasks with idle / finished remnants.

Let's add a bulk delete mechanism, similar to the one we have for workspaces. Please see this not-so-current mockup where I am also showing the future placeholder for Tasks delegation and Tasks pausing / stopping.