tissuenet model support and documentation

[lassedochreden]

Hi @Milad4849,

a few things and thanks a lot in advance for clarification:

1. I realized that for the cellpose-"flavours" of steinbock the "tissuenet" model is not supported (despite being the most relevant one for our IMC data I think). Will this be implemented anytime soon or did I miss it somehow? Also the default parameters for the other models may need adjustment, since the output masks do not look appropriate.

2. Better general documentation for the different "flavours" of docker images (cellpose / gpu / xpra etc.) would be helpful and would also make them easier to find.

3. Better documentation for some utility functions such as steinbock utils expand.