[Finishes #79484946] Free play links on student dashboard and puzzle headers

Links to the k1 version of Playlab and Artist free play when the user is in a k1 course.

![screen shot 2014-09-29 at 3 25 53 pm](https://cloud.githubusercontent.com/assets/413693/4450618/a12a4684-4827-11e4-83c8-b6cdf1cdc87c.png)

![screen shot 2014-09-29 at 2 37 00 pm](https://cloud.githubusercontent.com/assets/413693/4450623/afceaf36-4827-11e4-961d-3f893315baa3.png)

hm... this is repeated twice now. Maybe put this in ApplicationHelper at least?

This is also a bit fragile because it has a bunch of magic numbers that can change when scripts are edited (they  depend on the order of stages and levels -- so inserting or removing a level or stage before these levels will change the sequence).