Allow using as a staging source a Workflow Run RO-Crate

[jmfernandez]

The target here is just WfExS-backend should be able to consume its own RO-Crates, demonstrating true reproducibility.

This feature is divided in two milestones:

• Being able to reuse as much metadata as possible, so inputs, commits and containers are reused.
• Being able to reuse RO-Crate bundled copies of workflow, inputs and containers in the instantiation.

This last one can bring issues related to docker containers, as it might imply reassigning local container tags.