SSH service debugging and addtional information

* Changed ssh command log level from QUIET to FATAL. This will help
  users with debugging in case of errors related to SSH service.
  (See issues #112, #310)
* Added more information about SSH service in manual page. For SSH
  service to work, sshd server needs to be running on local system
  and must be configured to accept password authentication.

shellinabox/service.c

@@ -163,7 +163,7 @@ void initService(struct Service *service, const char *arg) {
 //          feature, we cannot be sure that it is available on the
 //          target server.  Removing it for the sake of Centos.
 //          "-oVisualHostKey=no"
-	  " -oLogLevel=QUIET %%s@%s", host);
+          " -oLogLevel=FATAL %%s@%s", host);
     free(host);
   } else {
     service->useLogin                       = 0;

shellinabox/shellinaboxd.man.in

@@ -497,6 +497,10 @@ to saying
 or
 .BR --service=/:SSH ,
 respectively.
+
+Please note that for SSH service to work properly, we need a running ssh server on
+local system with enabled password authentication.
+
 .RE
 #ifdef HAVE_OPENSSL
 .TP