Operational options: add initfiles

[alintulu]

Add operational option initfiles that people can use in their reana.yaml, similarly to the options initdir and toplevel. initfiles expects an array of files to read the input parameters from.

Example

inputs:
  options:
    initfiles: 
      - workflow/yadage/input_filenames.yml
      - workflow/yadage/input_cross_sections.yml

closes reanahub/reana#305

[diegodelemos]

Normally list comprehensions look more complicated than they should, but I feel in this case it would be more illustrative than the explicit loop:

operational_options["initfiles"] = [
    os.path.join(workflow_workspace, initfile) for initfile in operational_options.get("initfiles", [])]

There is no need to change anything if you don't think the same after reading the comment :)

[alintulu]

I actually prefer list comprehensions, not sure why I didn't think of it here :) I'll change it.

[diegodelemos]

All works nicely. Just making Travis pass left :)

[mvidalgarcia]

All works nicely. Just making Travis pass left :)

I think the travis issue happens because we have checksumdir pinned in reana-commons (checksumdir>=1.1.4,<1.2) and packtivity has it unpinned so it installs 1.2. There're two options:

• Bump checksumdir version to 1.2 in reana-commons and check that everything works fine.
• Pin checksumdir in reana-workflow-engine-yadage to be <1.2

[tiborsimko]

• Can you please add yourself to the AUTHORS.rst file?

• Can you leave a one-line note in CHANGES.rst about this change?