Normalising config directory to ensure it has trailing path separator resolving #2552

* Moved Setter next to Getter
* Set `config_dir` to ensure consistent directory for all files resolving #2551
* Changed PluginManager loading log message to include directory

PluginManager.h

@@ -52,4 +52,6 @@ private:
 
     RemovePluginCallback    RemovePluginCallbackVal;
     void *                  RemovePluginCallbackArg;
+
+    const char *            plugins_path = "plugins/";
 };