Support reading the KML Model tag

REVIEW: 110403
REVIEW: 108405
CCBUG: 318288
No more #ifdef DEBUG_TAGS
Cast sanity check in debug mode
Must not implicitly cast static_cast result to boolean
Store time resolution. Fix utc offset mixup. Add test case.
Fix timestamp parsing. Add test case.
It's either camera or lookat, so reuse m_abstractView. Const correct.
Add time primitives
Support reading gx:TimeSpan and gx:TimeStamp

REVIEW: 108388
Avoid name clash.
Show segment labels by default
install headers needed by GeoDataAbstractView.h
Fix capitalization according to kml spec.
KML Model tag writer.

REVIEW: 110509
BUG: 318288
Fix include guard
pass a const reference
cleanup forward declarations, friend declarations and includes in GeoDataFeature
check node type before casting KML feature to placemark

* also print a warning when unknown KML tag is encountered
* fixes crash introduced in commit 8ee588969b41890a6bd90f9b45eeb85658edf84f

BUG: 320056
fix initialization order
have GeoDataTourPrimitive and GeoDataPlaylist inherit from GeoDataObject rather than from GeoDateFeature

* both extend Object according to the KML spec