AJCC M Descriptor Code Cleanup

ajcc6_m ajcc6_mdescriptor ajcc6_mdescriptor stor_ajcc6_mdescriptor Description
<Any value> ERROR <BLANK> <BLANK> If M Descriptor is an error, both should be set to blank
NA <Any value> <BLANK> N For M values of NA
<BLANK> <Any value> <BLANK> <BLANK> For missing M values caused by an ERROR in mets
<Any value> <Any value> MATCH MATCH For all other cases, leave codes as they are