Configure things that should be configurable

[officialyinsane]

Identified in : #69

For example AsyncConfig.taskScheduler() currently uses a magic number for the thread count, and has a TODO statement on it.

I'd personally also like config to be fetchable from an endpoint (IIRC, actuator can do it for us), and the option for config to be edited in real time, without requiring application restart. But both of these should be considered "Nice to haves"

[pveeckhout]

I suggest using something in the line of spring cloud config
https://docs.spring.io/spring-cloud-config/docs/current/reference/html/