Redefine the metasplit calls to be more specific

[MrHedmad]

Currently we do a broad overview over the different tissues of origin, putting together different types of cancer that might have clinically and functionally little in common.

The metasplit calls that we use right now are suitable for a broad overview of the issue, but the results are currently not well curated. Make a new list with just the following cancer types:

• Breast adenocarcinoma;
• Colorectal adenocarcinoma;
• Prostate adenocarcinoma;
• Lung adenocarcinoma;
• Breast invasive carcinoma;
• Bladder urothelial carcinoma;
• Melanoma;
• Skin squamous cell carcinoma;