Refactor gene information interfaces

[holtgrewe]

Is your feature request related to a problem? Please describe.
The current gene information retrieval interfaces are a bit problematic. See below.

Describe the solution you'd like
Adjust them as follows:

• do not return maps from HGNC ID to information but rather lists of information objects with HGNC ID being a member
• retrieve "slimmer" version by default
• allow to switch on / off certain sections so not the full information is retrieved
• store "id only" information in an additional column family for faster iteration
• make all data structures on the interfaces to external protocol buffers
• implement pagination for retrieving genes

Describe alternatives you've considered
N/A

Additional context
N/A