consider if spring is ok dependency

[codefromthecrypt]

We currently have a hard-coded way to setup zipkin config. If spring is ok to run inside cassandra (just spring is needed, not spring boot), we can configure all the things, including sampling rate etc, without a lot of copy/paste. For example, this is how the Dubbo framework configures itself..

https://github.com/openzipkin/brave/tree/master/spring-beans

cc @jake-codes @llinder @michaelsembwever

[codefromthecrypt]

note: this could also be done as a separate module really..