Part 1 of 'force students' implementation in GUI

-GUI now opens new east panel when prompted (by a button).

-This panel contains radio boxes and JComboBoxes (populated with all
students) along with a button that will be responsible for altering the
graphs.

-this panel can also be made invisible when prompted (by the same
button used to open it).

-Fixed bug, so now if the teacher enters a non-parseable string (to be
converted to int for the team sizes), then an error message occurs and
the process is stopped.