Update datasources.tsv

[DeniseSl22]

There are quite some outdated/deprecated example mappings in the datasources.txt file. Several issues have been filled on that matter:

• [x] bridgedb/datasources#3
• [ ] bridgedb/datasources#4
• [x] bridgedb/datasources#8
• [ ] bridgedb/BridgeDb#15
• [ ] bridgedb/datasources#7
• [ ] bridgedb/BridgeDb#33
• [ ] bridgedb/BridgeDbWebservice#29
• [x] bridgedb/datasources#6

So, time to clean up that mess (perhaps make a "deprecateddatasources.txt file, to keep track?). @egonw suggested to test the linkouts automatically to see if they resolve.

[ariutta]

A semi-related issue: datasources.txt vs. datasources.tsv.