XD-1378: Add HttpClientProcessorOptionsMetadata
XD-1401 Add reactor-tcp Source and Througput Sink

Added reactor-tcp source module definition. Updated NetServer configuration to use individual properties that can be referenced from the CLI using OptionsMetadata.

Also addresses XD-1407 by adding a simple ThroughputSamplerMessageHandler that counts messages and reports throughput by recognizing demarcation/control messages. The message payloads are configurable but the default is to count messages between START and END messages.
Refactor imap into mail source
Creations options for mail sink
Make ContainerRegistrar ApplicationContextAware

- Fire ContainerStartedEvent only if the application context is
the Container context