Seamless terrain.

Heights, sizes and materials on the edges of terrains are corrected.


Before patch (4 terrains)
![image](https://f.cloud.github.com/assets/311074/1994033/62203cc4-84e5-11e3-8fdc-e396d80e1f1d.png)


After patch
![image](https://f.cloud.github.com/assets/311074/1994039/6afc61ba-84e5-11e3-993b-c1c059e3f39e.png)


[Test level](https://drive.google.com/file/d/0B4G7HDT9STV-ZDFrUmg3eDd5eHc/edit?usp=sharing) (extract to the folder 'game/levels/test'). Smart run from the command line
> application.exe -level "test/seamless-terrain/test1.mis"