rpc: Make logging RPC public

This started out as a developer hack but now it's useful
enough for general use. Unhide the call by moving it to `control` category.
This makes it documented in `help`.

src/rpc/misc.cpp

@@ -608,6 +608,7 @@ static const CRPCCommand commands[] =
 { //  category              name                      actor (function)         argNames
   //  --------------------- ------------------------  -----------------------  ----------
     { "control",            "getmemoryinfo",          &getmemoryinfo,          {"mode"} },
+    { "control",            "logging",                &logging,                {"include", "exclude"}},
     { "util",               "validateaddress",        &validateaddress,        {"address"} }, /* uses wallet if enabled */
     { "util",               "createmultisig",         &createmultisig,         {"nrequired","keys"} },
     { "util",               "verifymessage",          &verifymessage,          {"address","signature","message"} },
@@ -617,7 +618,6 @@ static const CRPCCommand commands[] =
     { "hidden",             "setmocktime",            &setmocktime,            {"timestamp"}},
     { "hidden",             "echo",                   &echo,                   {"arg0","arg1","arg2","arg3","arg4","arg5","arg6","arg7","arg8","arg9"}},
     { "hidden",             "echojson",               &echo,                   {"arg0","arg1","arg2","arg3","arg4","arg5","arg6","arg7","arg8","arg9"}},
-    { "hidden",             "logging",                &logging,                {"include", "exclude"}},
 };
 
 void RegisterMiscRPCCommands(CRPCTable &t)