External tilesets are sometimes not processed by default

[javagl]

One part of #61 was removing the quiet:boolean parameter that determined whether certain console.log messages should be printed, and replacing that with the logger. This flag was supposed to be removed in 42c0436 , but unfortunately, there's another boolean flag for the tile content processing, namely processExternalTilesets:boolean, and this led to a state where in some places, a quiet:false was passed in, and now interpreted as processExternalTilesets:false (for example, in the TileContentProcessing class).

(This is already fixed with 90a7b04 as part of #75 )