GPXIN-26: Calculate Min/Max Lat and Lon and add to Stats

Need to know more about the use-case the user has in mind, do they want the actual coordinates for max/min (so an actual lat/lon pair) or are they simply interested in extracting the maximum/minimum recorded latitude - essentially meaning those stats properties will simply be decimal.

One option might be to make the relevant stats property an object in itself, so we'd have something like

$stats->maxLon->Lon = 1234
$stats->maxLon->Lat = 4567
$stats->maxLat->Lon = 1134
$stats->maxLat->Lat = 5567

Which would give the option of either, but then when retrieving it you'd have to do something like

$foo = $o->getStats('MaxLon');
echo $foo->Lon;

Which feels a bit ugly and un-necessary

The user has said they need square bounds on a per-file, per-track and per-segment basis. Makes sense, it'd allow you (for example) to easily extract the bounds to pass into Google Maps to ensure it's correctly centred around the track you're displaying.

Commit 6d9e313 implements bounds calculations for the overall file, and also on a per-segment basis, so we just need to calculate per-track now.

We now have a bounds object within the stats for
- the entire file
- each track
- each segment

Running a print_r() on each gives

gpx->getJourneyStats()
stdClass Object
(
    [trackpoints] => 778
    [recordedDuration] => 7556
    [segments] => 16
    [tracks] => 16
    [maxacceleration] => 0
    [maxdeceleration] => 0
    [minacceleration] => 0
    [mindeceleration] => 0
    [avgacceleration] => 0
    [avgdeceleration] => 0
    [speedUoM] => Array
        (
        )

    [timeMoving] => 0
    [timeStationary] => 0
    [timeAccelerating] => 0
    [timeDecelerating] => 0
    [distanceTravelled] => 0
    [bounds] => stdClass Object
        (
            [Lat] => stdClass Object
                (
                    [min] => 56.114105
                    [max] => 56.179494
                )

            [Lon] => stdClass Object
                (
                    [min] => 43.346461
                    [max] => 43.522420
                )

        )

    [start] => 1368860043
    [end] => 1368888867
)

gpx->getStats('journey0')
stdClass Object
(
    [journeyDuration] => 1562
    [maxacceleration] => 0
    [maxdeceleration] => 0
    [minacceleration] => 0
    [mindeceleration] => 0
    [avgacceleration] => 0
    [avgdeceleration] => 0
    [speedUoM] => Array
        (
        )

    [timeMoving] => 0
    [timeStationary] => 0
    [timeAccelerating] => 0
    [timeDecelerating] => 0
    [distanceTravelled] => 0
    [bounds] => stdClass Object
        (
            [Lat] => stdClass Object
                (
                    [min] => 56.114105
                    [max] => 56.119712
                )

            [Lon] => stdClass Object
                (
                    [min] => 43.503630
                    [max] => 43.522420
                )

        )

    [start] => 1368860043
    [end] => 1368861605
    [recordedDuration] => 1562
    [elevation] => stdClass Object
        (
            [max] => 129.22
            [min] => 60.83
            [avgChange] => 0.38
        )

)

gpx->getStats('journey0','seg0')
stdClass Object
(
    [distanceTravelled] => 0
    [bounds] => stdClass Object
        (
            [Lat] => stdClass Object
                (
                    [min] => 56.114105
                    [max] => 56.119712
                )

            [Lon] => stdClass Object
                (
                    [min] => 43.503630
                    [max] => 43.522420
                )

        )

    [start] => 1368860043
    [end] => 1368861605
    [journeyDuration] => 1562
    [elevation] => stdClass Object
        (
            [max] => 129.22
            [min] => 60.83
            [avgChange] => 0.38
        )

    [timeMoving] => 0
    [timeStationary] => 0
    [timeAccelerating] => 0
    [timeDecelerating] => 0
)

I've updated the documentation (https://www.bentasker.co.uk/documentation/development-programming/222-php-gpx-ingest) to reflect the change to the stats objects