Change default parameters in interactive
Ensure correct sorting of images for viewer
Bug fix: Do not increase gain in centro-telo img

The docstring of ``encode_centro_telomeres_multichannel`` correctly
described the encoding as ranging from 0 to 3. However, I later
multiplied the image by 64 to make it visible, breaking the interface
(which other tools depended on for computing correct visibility). This
commit reverts that change.
Refactor interactive for a thinner main wrapper