Support new "heading" tag from osmand tracker plugin

Note that osmand now supports to track the heading in an "extension": (Needs to be explicitly enabled in the settings of the tracker plugin)

<trkpt lat="4X.XXXXXXX" lon="1X.XXXXXXX">

    <ele>XXX.XXX</ele>
    <time>2020-04-03T13:03:47Z</time>
    <hdop>7.504</hdop>
    <extensions>
        <speed>1.24</speed>
        <heading>233</heading>
    </extensions>

</trkpt>

1. Please support taking the direction from that.
2. To correct for phone/camera alignment issues, it might be possible to use the (smoothened) direction from the "next" point as a comparison and filter accordingly. This might enable to correct e.g. a constant offset, if a separate camera is mounted in a fixed angle to the phone, and it might be able to detect if both do not fit at all and throw an error. Or it might correct for magnetic errors due to large metal objects (car). Maybe a kalman filter could be useful here.

Start by reviewing the existing OsmAnd tracker-plugin handling and how direction is currently obtained. Confirm support for the value in the supplied example, then add coverage for that input and verify the resulting direction. Treat alignment correction and filtering as separate design questions, since the issue only proposes them.