Filled out the functionality of the OpenVideoButtonActionListener. A
user can now select a video file in the VideoFileChooser, it is checked
to make sure it is a valid file then the Video is set to the
VideoMatriarch. If it is not a valid file then a NullVideo is set to the
VideoMatriarch.

Signed-off-by: Theo Chupp <chuppthe@msu.edu>