Transaction exporter tool

[td202]

Purpose

A tool that dumps a transaction (specified by hash) from the chain to a file.

Changes

• Add dump-transaction.
• Enable CI.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.