The progress tracker API lets you model a tree of steps, along the same structure as protocols and subprotocols. Each step has an (optionally changing) label, and thus progress trackers can be arranged in a tree. Updates to the progress at each level flow up the tree via an RxJava observable (I guess we will use this more in future).
A simple console renderer is provided that uses ANSI escapes and Emoji to show animated progress through a protocol.
The trader demo is enhanced to use this framework, when run outside of Gradle.
* Dependency resolution/checking is now working on both sides of the two party trading protocol.
* The commercial paper contract was changed to check timestamping authority identities by name instead of key.
* The trader demo has been rewritten to use the protocol framework, which simplifies the code.
This commit is incomplete: only the seller side currently checks. The code will be refactored out into subprotocols in further commits.
Note that timeouts are currently unhandled.
