core: Removed unused class.

license_usage.java was not being used.

Change-Id: I1a6d595ad52b184c4e088ef6b61495128c4f0f74
Signed-off-by: Sharad Mishra <snmishra@linux.vnet.ibm.com>
Signed-off-by: Laszlo Hornyak <lhornyak@redhat.com>