Temporary fix huge terrain slots

Sometimes the slots provided by the paging terrain manager
are huge and no heightmap exists. This temporary fixes this so
that if it is too big, it at least does not crash.
Fix Buildsystem to support Debug Builds

Now the libraries are assigned correctly to each Build type.
Readme was updated to include those changes. Also added
libprotobuf, which will be required shortly.
Fix Debug Build error with OGRE_NEW

Change from OGRE_NEW to new, as when building in Debug mode, a error is happening with those classes.
Increase Terrain slots, change Texture

Increase Terrain slots as the size of each slot has been reduced previously
Also change the texture to grass, as it looks nicer then dirt