request for input: direction-finder mavlink message

[Jonathan Challinger]

This is a mavlink message for direction finders. This mean IR-lock for now.

        <message id="227" name="DIRECTIONFINDER">
            <description>Direction finder reporting</description>
            <field name="dir_body_x">x component of body-frame unit vector towards target</field>
            <field name="dir_body_y">y component of body-frame unit vector towards target</field>
            <field name="dir_body_z">z component of body-frame unit vector towards target</field>
            <field name="dir_ned_n">north component of NED-frame unit vector towards target</field>
            <field name="dir_ned_e">east component of NED-frame unit vector towards target</field>
            <field name="dir_ned_d">down component of NED-frame unit vector towards target</field>
            <field name="distance" type="float">distance to target in meters, -1 if inapplicable</field>
            <field name="target_ang_size">angular size of the target. 0 if inapplicable.</field>
        </message>