protected void setBottomLod(int bottomLod) {
        this.bottomLod = bottomLod;
    }
Stores a terrain patch's details so the LOD background thread can update
the actual terrain patch back on the ogl thread.

@author Brent Owens
jme3-terrain/src/main/java/com/jme3/terrain/geomipmap/UpdatedTerrainPatch.java