Do not write discarded tiles to TileConfiguration.registered.txt

[imagejan]

When a tile is discarded during stitching, this tile will only be ignored in the current stitching run, but it's image name and the coordinates (0.0, 0.0, 0.0) are recorded in the TileConfiguration.registered.txt file that is written on disk.

This behavior breaks workflows where the tile configuration is calculated from one set of images and subsequently applied to other sets (e.g. channels) without re-computing the overlap.
(Filtering the (0.0, 0.0, 0.0) positions would not work, since there always is one image that truly belong to this origin position.)

The discarded tile information should either not be written to the configuration file at all, or be marked as ignored. (See also the related issue #10)

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/stitch-then-split-large-round-field-in-fiji/41049/6