Add janis check for evaluating system compatability

[illusional]

It would be useful to run some diagnostic to confirm that Janis can run a workflow using the current configuration on a system. There are probably two levels:

Quick diagnostic:

• Ensure relevant software is loaded:
  • Make sure the container environment is loaded
  • Ensure java is loaded if using Cromwell

Deeper diagnostic:

• Quick diagnostic
• End-to-end run of example pipeline