Renamed goaltasks table to tasks

- Removed the difficulty field from the table
- Renamed column number to sort_order

Signed-off-by: Prashant Shah <prashah360@gmail.com>
Load 'Js' helper from AppController

Signed-off-by: Prashant Shah <prashah360@gmail.com>
Bug fix : Check user_id is null rather than goal_id

Signed-off-by: Prashant Shah <prashah360@gmail.com>