exercise - fix links on dash to direct to exercise taking;  treehelper - set of utility functions 

- Added dash links for taking an exercise.
- Load question result in html dataset.
- Starburst button will take practice exam at proper path.
The most basic reason to drop the DAO instance is so we can set fields on the object. If we don't drop, the DAO instance is not configurable by default which makes it very dificult to set object properties. Will add better reasoning to docs.