Support for TiledNdArray objects which are subsets of a larger Tileset

To get the full caching benefits that Tilesets provide it would be useful if TiledNdArray objects could describe a subset of the tiles generated for larger areas, this would allow reuse of existing tiles by CoverageJSON responses for sub regions of larger datasets.

One way this could be acheived would be to add an optional origin member to the TiledNdArray object, this would be an integer array of the same shape as the tileShape member which would describe the origin index values for a TileSet. The values provided by the origin member could then be used by CoverageJSON clients to adjust the values provided by the tileShape member so that they described a subset of the larger tileset. If an origin member was not specified a client would treat the origin values for all dimensions to be zero.

Beginne damit, die Definitionen von TiledNdArray und tileShape in der CoverageJSON-Spezifikation zu finden. Überprüfe, wie CoverageJSON-Clients tileShape interpretieren, und ermittle, wie ein optionales origin-Member eine Teilmenge eines größeren Tileset beschreiben würde. Als erledigt gilt die Aufgabe, wenn die Spezifikation origin, seine Form und die Standardwerte null sowie das daraus resultierende Client-Verhalten eindeutig definiert.