MXS-1220: Implement /maxscale/ resource

The resource exposes the various directories that MaxScale uses. Further
information, like uptime, could be added at a later point.

include/maxscale/config.h

@@ -23,6 +23,7 @@
 #include <sys/utsname.h>
 
 #include <maxscale/modinfo.h>
+#include <maxscale/jansson.h>
 
 MXS_BEGIN_DECLS
 
@@ -395,4 +396,12 @@ void config_disable_feedback_task(void);
  */
 bool config_reload(void);
 
+/**
+ * @brief List all path parameters as JSON
+ *
+ * @param host Hostname of this server
+ * @return JSON object representing the paths used by MaxScale
+ */
+json_t* config_paths_to_json(const char* host);
+
 MXS_END_DECLS