Auto Detect TaskType

# References
* https://www.pivotaltracker.com/story/show/81061674

# Major Changes
* Convert TaskType from an ActiveRecord model to a standard ruby class
* Rails will register existing task types automatically
* Simplified Task by removing the magic class variables for title and role as well as the initializer for defaulting title and role
* Updated generator so that new Tasks created by generator automatically registers

# Gotchas
* Be sure in future tests when you create an instance of a Task that you give it a title and role

--- FF + AC