Batch event tap writes

Prior to this change, the event tap system sent each event to the
registered taps individually; the network overhead in this single
thread caused the event tap queue to back up and events to be
lost.
[maven-release-plugin] prepare release 1.14.30
[maven-release-plugin] prepare for next development iteration
[maven-release-plugin] prepare release 1.14.31
[maven-release-plugin] prepare for next development iteration
[maven-release-plugin] prepare release 1.14.32
[maven-release-plugin] prepare for next development iteration
Upload failed batches
[maven-release-plugin] prepare release 1.14.33
[maven-release-plugin] prepare for next development iteration
[maven-release-plugin] prepare release 1.14.34
[maven-release-plugin] prepare for next development iteration
Change retry logic for failed uploads
[maven-release-plugin] prepare release 1.14.35
[maven-release-plugin] prepare for next development iteration
Extract EventTapWriter.EventFlow into its own class

EventFlow is no longer an inner class of EventTapWriter but is now its
own independent class: EventTapFlow.

EventTapWriter was also furnished with unit tests.

The licence was updated for all files.
Refactor the interaction between EventTapWriter and BatchProcessor

- Create a BatchProcessorFactory to generate new BatchProcessor objects
- Move logic for cloning batches to multiple taps into the new
  BatchCloner class.
- Create BatchProcessor objects based on need, to avoid queuing up
  events that have no associated tap.
Refactor the interface between EventTapWriter and EventTapFlow

- Create EventTapFlow objects using Guice.
- Decouple the BatchProcessor from the counters.
- Improve testability of EventTapWriter.
Support EventTapFlow with QoS requirements.

Each flow now has its own BatchProcessor (queue and thread) to further
reduce interference between taps of the same type. The EventTapWriter
will also respond to "qos" property of a tap by creating a special QoS
tap (which, for now, is just a normal EventTapFlow object).
[maven-release-plugin] prepare release 1.14.36