split terrain sources: generator/elemateterrain, move to terrain  subfolder #14
Merge remote-tracking branch 'origin/navigation_enhancement' into landscape_14
Merge branch 'master' into landscape_14
restructuring terrain creation to make landscape creation and update easier #14

do all the creation with physx heightfield samples and copy the data in the end to osg, all in one step
add river course #14
add Elements class to hold material defs for physx and texturing

currently with default physx material
add shading material uniforms #14
add water terrain level (additional tile) and some more materials #14
let ElemateTerrain::heightAt() support multiple terrain levels #14
set water alpha blending #14
Merge branch 'master' into landscape_14
add dedicated water shader #14
create terrain type texture only for base level tile #14
change geometry shader file ext to geom, to conform with osg
add rock terrain texture #14
pass global and game time to shader
add waves to water terrain shading #14
scale rock texture to 1024, to be more compatible with osg #14
fix CMakeLists.txt #14
improve the soundmanager and background sound
- make background sound non-3D
- fixed some bugs
- insert comments