Add accessability labels to Task list, Task addition

Added an accessibility label to the task list.  The label will allow
Voice Over users to hear their tasks spoken to them, and also provide a
hook for testing frameworks.

Labels are composed of the priority, task, and due date, the full
version being 'Priority B, Complete Tax Return, Due Tomorrow".

Added the accessability label "Task Details" to the text field in the
"Add Task" view.