Add "complete and duplicate" to task actions

For tasks that get done over the course of multiple sessions, it would be useful to have a task command that would mark the current task complete, and create a new copy of the task with the same text+import/urgent+time properties. Perhaps the command could be `!next` or `!tobecontinued` or just `!continue`, what do others think?

The salient differences between the duplicated task and the original:
1. Duplicated task will have a blank Start Date, if one had been present on the original completed task
2. Reset Task Score, if the original task had accumulated a Task Score prior to being completed

This task command could also be useful when I have a collaborative list with questions to me: I could mark the original question task complete (so I get my hit of endorphins from completing something), and create a copy of the task that I could then forward back to the original task creator with my answer to the question.