Reworked show_tasks_by_priority() and speak_task()

Reworked: `show_tasks_by_priority()`, `speak_task()` and `self.lang_list`

I left the old version of `show_tasks_by_priority()` in triple quotes to allow for experimentation, verification.  I may safely be removed.

Also opened an issue on `speak_task()` when starting task id != 1.