Morphing experiments
Detail texture
Add osgEarthUtil::DetailTexture
add noise tex
Make mp the default terrain engine
Merge branch 'master' into topic-morphing
Experiments in LOD morphing with elevation_tile_size
merge master
Fix compile error after master merge
merge
Merge branch 'master' into topic-morphing

Conflicts:
	src/applications/osgearth_viewer/osgearth_viewer.cpp
	src/osgEarthDrivers/engine_mp/MPTerrainEngineNode.cpp
	src/osgEarthDrivers/engine_mp/TileModelCompiler.cpp
	src/osgEarthUtil/CMakeLists.txt
	tests/feature_tfs.earth
	tests/readymap.earth
merge
LOD morphing: improvements, fix to HeightField resampler.
Fix #308 Crash in mask code in MP driver
Add support for ImageLayer 'sharing' in MP engine GPU processing
add layout to TextSymbol
add layout to TextSymbol
Update AnnotationUtils.cpp
add layout to TextSymbol
Add HTMGroup