- Apply "Level of details (LOR)" while parsing kml placemarks

- Parsing of kml document from QIODevice

- Integration of KMLDocument with PlaceMarkPainter for initial support of kml placemarks

- Apply KMLFolder object to act as a layer

- Initial support of KML style objects (icon style, label style)

- Integration with Digikam. This includes test of kml output of Digikam on Marble

- Sort placemarks while parsing them from input kml stream. This will speed up drawing of placemarks. (Regionator)

- Serialization of in memory kml document structure to disk cache. Introduce options like:
    * memory cache size
    * disk cache size
this will allow to store a big kml documents and efficient memory usage.

- Show list view on the left that indicates opened kml/gpx files. List view should only
  appear if there are more than one opened file.

Enhancements:
- Use pointer to character parsing function instead of switching m_phase in KML parsers to speed up parsing