libavg_app: clearer CLI help for undefined params
libavg_app: clearer CLI help for undefined params

svn path=/branches/libavg_app/; revision=9037

libavg/libavg,hoodie/libavg,yyd01245/libavg,libavg/libavg,hoodie/libavg,th3infinity/libavg,yyd01245/libavg,yyd01245/libavg,scotty007/libavg,hoodie/libavg,th3infinity/libavg,scotty007/libavg,libavg/libavg,scotty007/libavg,scotty007/libavg,th3infinity/libavg,hoodie/libavg,th3infinity/libavg,libavg/libavg,yyd01245/libavg