New virtual for APM style mission support

src/FirmwarePlugin/APM/APMFirmwarePlugin.cc

@@ -378,3 +378,9 @@ void APMFirmwarePlugin::setSupportedModes(QList<APMCustomMode> supportedModes)
 {
     _supportedModes = supportedModes;
 }
+
+bool APMFirmwarePlugin::sendHomePositionToVehicle(void)
+{
+    // APM stack wants the home position sent in the first position
+    return true;
+}

src/FirmwarePlugin/APM/APMFirmwarePlugin.h

@@ -87,7 +87,8 @@ public:
     virtual int manualControlReservedButtonCount(void);
     virtual void adjustMavlinkMessage(mavlink_message_t* message);
     virtual void initializeVehicle(Vehicle* vehicle);
-    
+    virtual bool sendHomePositionToVehicle(void);
+
 protected:
     /// All access to singleton is through stack specific implementation
     APMFirmwarePlugin(QObject* parent = NULL);

src/FirmwarePlugin/FirmwarePlugin.h

@@ -96,6 +96,14 @@ public:
     
     /// Called when Vehicle is first created to send any necessary mavlink messages to the firmware.
     virtual void initializeVehicle(Vehicle* vehicle) = 0;
+
+    /// Determines how to handle the first item of the mission item list. Internally to QGC the first item
+    /// is always the home position.
+    /// @return
+    ///     true: Send first mission item as home position to vehicle. When vehicle has no mission items on
+    ///             it, it may or may not return a home position back in position 0.
+    ///     false: Do not send first item to vehicle, sequence numbers must be adjusted
+    virtual bool sendHomePositionToVehicle(void) = 0;
     
 protected:
     FirmwarePlugin(QObject* parent = NULL) : QGCSingleton(parent) { }

src/FirmwarePlugin/Generic/GenericFirmwarePlugin.cc

@@ -110,3 +110,11 @@ void GenericFirmwarePlugin::initializeVehicle(Vehicle* vehicle)
     
     // Generic Flight Stack is by definition "generic", so no extra work
 }
+
+bool GenericFirmwarePlugin::sendHomePositionToVehicle(void)
+{
+    // Generic stack does not want home position sent in the first position.
+    // Subsequent sequence numbers must be adjusted.
+    // This is the mavlink spec default.
+    return false;
+}

src/FirmwarePlugin/Generic/GenericFirmwarePlugin.h

@@ -46,6 +46,7 @@ public:
     virtual int manualControlReservedButtonCount(void);
     virtual void adjustMavlinkMessage(mavlink_message_t* message);
     virtual void initializeVehicle(Vehicle* vehicle);
+    virtual bool sendHomePositionToVehicle(void);
 
 private:
     /// All access to singleton is through AutoPilotPluginManager::instance

src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc

@@ -200,3 +200,10 @@ void PX4FirmwarePlugin::initializeVehicle(Vehicle* vehicle)
     
     // PX4 Flight Stack doesn't need to do any extra work
 }
+
+bool PX4FirmwarePlugin::sendHomePositionToVehicle(void)
+{
+    // PX4 stack does not want home position sent in the first position.
+    // Subsequent sequence numbers must be adjusted.
+    return false;
+}

src/FirmwarePlugin/PX4/PX4FirmwarePlugin.h

@@ -46,6 +46,7 @@ public:
     virtual int manualControlReservedButtonCount(void);
     virtual void adjustMavlinkMessage(mavlink_message_t* message);
     virtual void initializeVehicle(Vehicle* vehicle);
+    virtual bool sendHomePositionToVehicle(void);
 
 private:
     /// All access to singleton is through AutoPilotPluginManager::instance