Merge pull request #557 from XenonofArcticus/master

Documents sqlite dependency and osgearth_conv tool.
Splat: added manual bilinear filtering to the coverage data in the shader
Merge branch 'master' of github.com:gwaldron/osgearth
Controls: redo the resize handling so it doesn't rely on the RESIZE event
Incremental update: print out invalid tile warning
Fixed bug in createTile where it would crash if you requested a tile that had no data.
Merge branch 'master' of https://github.com/gwaldron/osgearth
Change to createTile to return NULL if a heightfield can't be created
Splatting: experimenting with detail splats and noise functions..
Splat: integrate noise based splatting tests
Merge branch 'master' of github.com:gwaldron/osgearth
ViewWidget: add support for FSAA in Qt widget
Logarithmic depth buffer: fixes to fragment clipping
Added quadkey driver to support bing maps style datasets
Docs for the quadkey driver
Removed invertY option from quadkey driver.
Splat: add detail support
fix
merge
Merge branch 'master' of github.com:gwaldron/osgearth