Java generator hard-codes sysid and compid

The Java code generator hard-codes a sysid of 255 and compid of 190, overwriting a user-specified sysid or compid. For example, this is the msg_heartbeat packing function:

public MAVLinkPacket pack(){
        MAVLinkPacket packet = new MAVLinkPacket(MAVLINK_MSG_LENGTH);
        packet.sysid = 255;
        packet.compid = 190;
        packet.msgid = MAVLINK_MSG_ID_HEARTBEAT;

        packet.payload.putUnsignedInt(custom_mode);

        packet.payload.putUnsignedByte(type);

        packet.payload.putUnsignedByte(autopilot);

        packet.payload.putUnsignedByte(base_mode);

        packet.payload.putUnsignedByte(system_status);

        packet.payload.putUnsignedByte(mavlink_version);

        return packet;
    }

This was most likely implemented because Java is typically used for a GCS, but that is not always the case. In my case, I am creating a mock drone in Java. It makes sense that these values could be used as defaults, but should not be hard-coded into packing functions.

My recommendation is to make these defaults in MAVLinkMessage, and remove them from the subclassed message packing functions.

ArduPilot / pymavlink

Java generator hard-codes sysid and compid #160