add freesurfer LUT index

Added these index to fslabel.mat 
---------------------
219 Cerebral_White_Matter                   
220 Cerebral_Cortex   
250 Fornix                                  
251 CC_Posterior                         
252 CC_Mid_Posterior                       
253 CC_Central                             
254 CC_Mid_Anterior                         
255 CC_Anterior