Rover: 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.

Rover/GCS_Mavlink.cpp

@@ -185,7 +185,7 @@ void GCS_MAVLINK_Rover::send_pid_tuning()
     Parameters &g = rover.g;
     ParametersG2 &g2 = rover.g2;
 
-    const AP_Logger::PID_Info *pid_info;
+    const AP_PIDInfo *pid_info;
 
     // steering PID
     if (g.gcs_pid_mask & 1) {