Initial support for multicore seeding
Merge remote-tracking branch 'origin/topic-multicoreseed'
Added documentation for new --threads and --estimate options.

Fixed warning message from osgDB
KML tweaks; depth offset support in FMG
Merge branch 'master' of github.com:gwaldron/osgearth
tweak to the overlaydecorator to ensure that depth field sampling penetrates the terrain
Fix top-level bounding sphere issue in FMG
Fixed TileCache driver to not be off by one lod.
Merge branch 'master' of https://github.com/gwaldron/osgearth
EarthManipulator updates.  Throwing support added and lots of touch control improvements.
Updated osgEarthViewerIOS to reflect latest EarthManipulator changes.
Merge branch 'master' of https://github.com/gwaldron/osgearth
Merged and tweaked changes from PR #350 - added multitouch twist support.  General touch control improvements as well.
Fix to HeightFieldUtils to work with a 2x2 hf (aroth)
Controls: fix minimum width bug
Fix: OD bug in which the RTT far plane passed the horizon plane
KML altitude mode fixes
OverlayDecorator fix - empty vertex set caused bad projection
doc updates
Memory fixes for TileIndex driver

Fixed the TileIndex driver so it doesn't need all of the images to be
precomputed.  It can composite as it is collecting now to avoid using
too much memory.
Also disabled the l2 cache on the cached GDAL TileSources to reduce
memory usage.