Added support for exporting logfile to KML. 

**WIP** waiting on KML

Currently the KML export settings are hardcoded, but these can be extended to be user selectable.

What can be seen in this screenshot is a UAV track for which the line color indicates the airspeed. There are also timespan points generated every 2 seconds which can be clicked on for further information. The below screenshot does not show all the info, I will provide an updated one tomorrow.

![0bzsmui](https://f.cloud.github.com/assets/1118185/650863/16cd1eb2-d465-11e2-9715-90e2198ecb52.png)

NOTE: This will not work without libkml, which will be the object of another PR.