Fixed tumor normal and RNAsum to use sequenced only library

[victorskl]

• Improved metadata lookup for WGS and WTS
• Added more test cases

Related #548

[reisingerf]

Hm, why move the retrieval/query logic into the metadata service?
It is quite specific to the respective service and I would have thought should be/stay in their control/responsibility?

[victorskl]

Yup. More for unit test-able purpose.

Business query to organised as box-function. Hopefully reusable (if any). But, yes, mainly for unit test / under radar for logic changes.

For example; RNAsum counterpart, I would not need to touch rnasum_step module (front controller) at all. As it delicates business logic into service layer i.e. "box function call" -- by looking at function name, you can hint roughly what it is doing; instead of more generic function; etc.