Copy last task

[jaragunde]

This feature would be useful for users who begin the day of work working on what they left the previous evening. They can already copy the previous day, then delete other tasks except the last and finally change its time, but that's not really convenient.

To define this task more formally:

• Add a button "copy last task" to the sidebar in the tasks page.
• This button would copy the latest task among the ones from the previous dates.
• The start/end times of the task would be cleared and cursor would be placed in the start time field.

[dmtrek14]

We are in the process of rewriting the frontend for tasks. Any outstanding bugs and enhancements for the old interface will be taken into account as we implement the new design.