More descriptive task output for package actions + action fixtures

Adding more detailed task output for package actions. Also there
are now helper methods to produce actions based on yaml fixtures,
which allows easier mocking.

The ideal combination of the action fixtures is this PR in Dynflow:

https://github.com/Dynflow/dynflow/pull/90

which makes the web console to use yaml as the format for showing
inputs/outputs of actions. So one can get new fixtures as easy as
perform the action though user interface and use the Dynflow console
to copy the fixture data.