Add AnnotationNode::getOrCreateAnnotationData
Added MapNodeHelper to osgearth_controls demo
Added check in ScriptEngineFactory to prevent repeated attempts at loading a scripting driver that fails.
FileSystemCache: added cache expiration support
Merge branch 'master' of github.com:gwaldron/osgearth
Merge branch 'upstream/master'

Conflicts:
	src/osgEarth/HTTPClient.cpp
	src/osgEarth/TerrainLayer.cpp