Merge remote branch 'upstream/master'
Added occlusion culling max altitude to IconSymbol; renamed elevation to altitude throughout OC code
Merge branch 'master' of github.com:gwaldron/osgearth
docs: update data sources
Update data.rst
Update data.rst
Fixed GPU clamping bug under MP, wherein the RTT depth camera was taking a picture of the right thing but at the wrong LOD.
FIX: empty VirtualProgram was not working properly; restore DepthOffset defaults.
Merge branch 'master' of github.com:gwaldron/osgearth
Commenting out troublesome warning.
Added option to disable collision avoidance feature in the EarthManipulator
Added needed call in the PolygonizeLinesFilter to add geometries to the feature index when appropriate.
Merge branch 'master' of https://github.com/gwaldron/osgearth
Added reference to gdal_data folder.
Merge branch 'master' of https://github.com/gwaldron/osgearth
Modified WFS MIME checks to allow for a subtype or optional parameter
Modified WFS MIME checks to allow for a subtype or optional parameter
Merge pull request #339 from jhgandhi/master

Modified WFS MIME checks to allow for a subtype or optional parameter
OverlayDecorator: add overlay graph bounds clipping; update overlayviewer to show it
Merge branch 'master' of github.com:gwaldron/osgearth