Improving readme and making SDK tweaks

Changes include:

- Usable README documentation 
- Deprecation of EpochCounter for EpochProcessor
- Rename of runner.register(Agent) -> runner.add(Agent)
- Rename agent.getComponentHumanLabel() -> agent.getAgentName()

Sidekick: @jstenhouse 
Doc Review: @barbnewrelic
FYI: @briandela @tmacie @serened