Fix isCapable for PX4 plugin

src/FirmwarePlugin/PX4/PX4FirmwarePlugin.cc

@@ -188,3 +188,8 @@ void PX4FirmwarePlugin::adjustMavlinkMessage(mavlink_message_t* message)
     
     // PX4 Flight Stack plugin does no message adjustment
 }
+
+bool PX4FirmwarePlugin::isCapable(FirmwareCapabilities capabilities)
+{
+    return capabilities == MavCmdPreflightStorageCapability;
+}

src/FirmwarePlugin/PX4/PX4FirmwarePlugin.h

@@ -38,7 +38,7 @@ class PX4FirmwarePlugin : public FirmwarePlugin
 public:
     // Overrides from FirmwarePlugin
     
-    virtual bool isCapable(FirmwareCapabilities capabilities) { Q_UNUSED(capabilities); return false; }
+    virtual bool isCapable(FirmwareCapabilities capabilities);
     virtual QList<VehicleComponent*> componentsForVehicle(AutoPilotPlugin* vehicle);
     virtual QStringList flightModes(void);
     virtual QString flightMode(uint8_t base_mode, uint32_t custom_mode);