Zipper tile creation (WIP)

.../orekit/rugged/intersection/duvenhage/MinMaxTreeTile.java

src/main/java/org/orekit/rugged/raster/SimpleTile.java

src/main/java/org/orekit/rugged/raster/TilesCache.java

src/main/java/org/orekit/rugged/raster/ZipperTile.java

src/test/java/org/orekit/rugged/raster/SimpleTileTest.java

src/test/java/org/orekit/rugged/raster/TilesCacheTest.java