Validate parameters before storing them

The runtime modification of servers, services and monitors now validates
the parameters before starting the update process. This guarantees that
the set of parameters is valid before it is processed.

After the validation, the parameters are now also stored in the list of
configuration parameters. This will simplify the serialization process by
removing the need to explicitly serialize all common object parameters.

server/core/internal/service.hh

@@ -59,10 +59,8 @@ public:
      *
      * @param name    Name of the parameter to update
      * @param value   The new value of the parameter
-     *
-     * @return True if the parameter and its value were valid
      */
-    bool update_basic_parameter(const std::string& name, const std::string& value);
+    void update_basic_parameter(const std::string& name, const std::string& value);
 
     /**
      * Set the list of filters for this service