Implemented following changes in users/workplan page
* Tasks page now redirects to workplan page.
* Workplan page displays "Recent work" and "Next tasks" list.
* Changed "-8 days" to "8 days ago".
* Rewrote TimeParser#format to support I18n and "spent" durations.
* Disabled sorting in "Recent work" list.
* Now time displayed in "Recent work" is spent time (before it was time "left").
* Removed "Tasks" from navigation links on user pages.
Completes https://squish.ish.com.au/tasks/17502