Log categories can now be added to and removed from

Also, set_log without parameters now prints the log categories

src/rpc/core_rpc_server.cpp

@@ -810,6 +810,7 @@ namespace cryptonote
   bool core_rpc_server::on_set_log_categories(const COMMAND_RPC_SET_LOG_CATEGORIES::request& req, COMMAND_RPC_SET_LOG_CATEGORIES::response& res)
   {
     mlog_set_log(req.categories.c_str());
+    res.categories = mlog_get_categories();
     res.status = CORE_RPC_STATUS_OK;
     return true;
   }