Add support for subtasks-file

This new keyword adds all the subtasks from another file on the same ref
as the parent task.

Change-Id: I2174ac16e9f964fc0f015d7c088dd69ae46074f0
5 files changed
tree: f58c572a07756c842fe4ff4708fda2b594fe4dc4
  1. src/
  2. test/
  3. .gitignore
  4. pom.xml