Change naming of Masks, Outlines and Distance Transformations for training

Currently during the training process, files for masks, outlines and distance transformations are generated and then sorted. If a tile is called "tile_01_132", the mask for example will be called "mask_01_132", same for outlines and dist trafo. This makes it difficult to combine different datasets, as it requires a) that all tiles have the same name ("tile..." and not e.g. "leipzig..." and "halle...") and b) makes it impossible to easily combine different datasets that follow the same numbering scheme (e.g. "leipzig" and "halle" can not both have a "01_01" tile).

My suggestion would be to follow the naming conventions of the labels, which have to be named "label_[tile_name]". So now, masks would be called "mask_[tile_name]" and so forth, so we can easily combine the different datasets into one big block.

An example:

• tile: "leipzig_15_13"
• label: "label_leipzig_15_13"
• mask: "mask_leipzig_15_13"
• outline: "outline_leipzig_15_13"
• disttrafo: "dist_trafo_leipzig_15_13"