Added makefile for downloading, building, and installing libkml.
Added support for exporting logfile to KML. Currently the KML export
settings are hardcoded, but these can be extended to be user selectable.
Reduce chances for a race condition by making the slot a direct connection.
Previously, at high parsing rates there was a risk that the parser outpace
the KML file generation, leading to lost frames if a PositionActual update
weren't acted on in a timely manner.
Implemented custom balloon style. This gets rid of the default "Directions
to here..." text.

Changed placemarks to use a style URL.
Changed auto-suggested export file name to match input file name.
Only export data when home location is set.
Added support for saving KMZ files.
Added a lot of new imagery to the KML export:

1) Ground path
2) Wall axes
3) Arrows which point in the vehicle's direction of movement
4) Extrusions to the ground.
Added 180 degrees rotation because arrow icon points down, i.e. south.
Added check for GPS availability before plotting points.
Swapped order between kml and kmz so that kmz is the default save option.
Added support for setting transparency.

Reordered style functions.
Logging: restore to next now kmlexport removed
GCS: Migrate kmlexport to its own plugin
Kml Export: commit missing file
KMLExport: disable for windows until libkml compilation is fixed.
Respond to review comments.
KmlExportPlugin: comments from review
KmlExport plugin: make this a compile time option

Until KML is merged and workign on everything we should make this
an optional component as we cannot count on the users having libkml
installed.  This makes this code mergable.
Added comments as requested in review.