Improved the usage messages of the cta-xrootd_plugins-XXXX commands

xroot_plugins/OpaqueQueryCmdLineArgs.cpp

@@ -106,6 +106,8 @@ OpaqueQueryCmdLineArgs::OpaqueQueryCmdLineArgs(const int argc, char *const *cons
 //------------------------------------------------------------------------------
 void OpaqueQueryCmdLineArgs::printUsage(std::ostream &os) {
   os <<
+    "Description:" << std::endl <<
+    "    Sends an xrootd \"opaque query\" message to the CTA front end" << std::endl <<
     "Usage:" << std::endl <<
     "    cta-xroot_plugins-opaque-query [options] ctaHost ctaPort queryFilename" << std::endl <<
     "Where:" << std::endl <<

xroot_plugins/WriteNotificationMsgCmdLineArgs.cpp

@@ -123,6 +123,8 @@ WriteNotificationMsgCmdLineArgs::WriteNotificationMsgCmdLineArgs(const int argc,
 //------------------------------------------------------------------------------
 void WriteNotificationMsgCmdLineArgs::printUsage(std::ostream &os) {
   os <<
+    "Description:" << std::endl <<
+    "    Writes a \"notification\" message to the specified file" << std::endl <<
     "Usage:" << std::endl <<
     "    cta-xroot_plugins-write-notification-msg filename" << std::endl <<
     "    cta-xroot_plugins-write-notification-msg -h|--help" << std::endl <<