Add creation and destruction of monitors

Monitors can now be created and destroyed at runtime. The configurations
for new monitors are persisted to disk.

include/maxscale/config_runtime.h

@@ -157,3 +157,23 @@ bool runtime_create_listener(SERVICE *service, const char *name, const char *add
  * @return True if the listener was successfully destroyed
  */
 bool runtime_destroy_listener(SERVICE *service, const char *name);
+
+/**
+ * @brief Create a new monitor
+ *
+ * @param name Name of the monitor
+ * @param module Monitor module
+ * @return True if new monitor was created and persisted
+ */
+bool runtime_create_monitor(const char *name, const char *module);
+
+/**
+ * @brief Destroy a monitor
+ *
+ * Monitors are not removed from the runtime configuration but they are stopped.
+ * Destroyed monitor are removed after a restart.
+ *
+ * @param monitor Monitor to destroy
+ * @return True if monitor was destroyed
+ */
+bool runtime_destroy_monitor(MONITOR *monitor);

include/maxscale/monitor.h

@@ -196,6 +196,7 @@ struct monitor
                                      * two times the option value.
                                      */
     MONITOR_OBJECT *module;       /**< The "monitor object" */
+    char *module_name;            /**< Name of the monitor module */
     void *handle;                 /**< Handle returned from startMonitor */
     size_t interval;              /**< The monitor interval */
     struct monitor *next;         /**< Next monitor in the linked list */
@@ -243,7 +244,7 @@ void mon_log_state_change(MONITOR_SERVERS *ptr);
 void mon_hangup_failed_servers(MONITOR *monitor);
 
 /**
- * @brief Serialize a monitor to a file
+ * @brief Serialize the servers of a monitor to a file
  *
  * This partially converts @c monitor into an INI format file. Only the servers
  * of the monitor are serialized. This allows the monitor to keep monitoring
@@ -258,6 +259,16 @@ void mon_hangup_failed_servers(MONITOR *monitor);
  */
 bool monitor_serialize_servers(const MONITOR *monitor);
 
+/**
+ * @brief Serialize a monitor to a file
+ *
+ * This converts the static configuration of the monitor into an INI format file.
+ *
+ * @param monitor Monitor to serialize
+ * @return True if serialization was successful
+ */
+bool monitor_serialize(const MONITOR *monitor);
+
 /**
  * Check if a monitor uses @c servers
  * @param server Server that is queried