Generations of students and parents have groaned over a chore essential for those who need assistance in paying for college: filling out the Free Application for Federal Student Aid. Some get stuck on what can be a complicated sequence of questions. Others miss deadlines or skip the process entirely.  Now, the government is taking a step meant to ease, if not eliminate, the pain of completing what is known as FAFSA. This week, it launched the first official mobile app to guide families through a task that is necessary for students seeking federal Pell Grants and most other forms of aid.