More changes to ensemble roll marking screens

1. In version 8.0.28 and above the student name and form now read directly from the Students file. If the Student leaves the school, the name will still be visible on the roll but it will be yellow-shaded and grey text.

2. NEW feature 
Click the rehearsal date (at the top of the attendance column) and it will show all ABSENCES for that date. Users can then click the email button at the top to email the found set of records. Click the red 'SHOW ALL' button to go back to the entire ensemble.