collector: builder style configs

* `CollectorServiceBuilder` now is the way to build a collector service
* Add `Adaptive`, `Adjustable`, `CollectorInterface` convenience functions for more intuitive configuration files.
* Update `collector-dev.scala`
* Add `collector-zk.scala` that uses Zookeeper for sample rate configuration
* Add `collector-zk-adaptive.scala`, same as above but with an adaptive sampler