cmd/rv: fixed profile.go and main.go file heaers including USAGE section in main.go

cmd/rv/main.go

@@ -27,6 +27,27 @@ LICENSE
 
   You should have received a copy of the GNU General Public License
   along with revid in gpl.txt. If not, see http://www.gnu.org/licenses.
+
+USAGE
+  There must firstly be a netsender configuration file under /etc/netsender.conf.
+  Example:
+
+  ma 00:00:00:00:00:01
+  dk 0
+  wi
+  ip V0, T0
+  op
+  mp 60
+  ap 0
+  tg
+  hw
+  sh vidgrind.appspot.com
+
+  Revid configuration is controlled by valid variables given values on netreceiver
+  or vidgrind interface. See revid/config for valid variables.
+
+  To run rv simply build and call:
+  ./rv
 */
 
 // revid-cli is a command line interface for revid.