AC_AutoTune: stop libraries including AP_Logger.h in .h files

AP_Logger.h is a nexus of includes; while this is being improved over
time, there's no reason for the library headers to include AP_Logger.h
as the logger itself is access by singleton and the structures are in
LogStructure.h

This necessitated moving The PID_Info structure out of AP_Logger's
namespace.  This cleans up a pretty nasty bit - that structure is
definitely not simply used for logging, but also used to pass pid
information around to controllers!

There are a lot of patches in here because AP_Logger.h, acting as a
nexus, was providing transitive header file inclusion in many (some
unlikely!) places.

libraries/AC_AutoTune/AC_AutoTune.cpp

@@ -1,6 +1,8 @@
 #include "AC_AutoTune.h"
-#include <GCS_MAVLink/GCS.h>
+
+#include <AP_Logger/AP_Logger.h>
 #include <AP_Scheduler/AP_Scheduler.h>
+#include <GCS_MAVLink/GCS.h>
 
 #define AUTOTUNE_PILOT_OVERRIDE_TIMEOUT_MS  500     // restart tuning if pilot has left sticks in middle for 2 seconds
 #if APM_BUILD_TYPE(APM_BUILD_ArduPlane)

libraries/AC_AutoTune/AC_AutoTune_Heli.cpp

@@ -19,6 +19,8 @@
 
 #include "AC_AutoTune_Heli.h"
 
+#include <AP_Logger/AP_Logger.h>
+
 #define AUTOTUNE_TESTING_STEP_TIMEOUT_MS   5000U     // timeout for tuning mode's testing step
 
 #define AUTOTUNE_RD_STEP                  0.0005f     // minimum increment when increasing/decreasing Rate D term

libraries/AC_AutoTune/AC_AutoTune_Multi.cpp

@@ -1,5 +1,7 @@
 #include "AC_AutoTune_Multi.h"
 
+#include <AP_Logger/AP_Logger.h>
+
 /*
  * autotune support for multicopters
  *