Add guidance on how to use wft4galaxy in PhenoMeNal without actually adding the workflow logic to wft4galaxy

[pcm32]

Hi guys,

I think that we should start using the workflow logic separate from wft4galaxy, so that this can ship as well as a PhenoMeNal independent product (we can still leave some examples of course based on PhenoMeNal). For this to happen I think that we need to add something in the documentation showing how to make this work. Then we could have phenomenal workflow-fluxomics-stationary, workflow-sacurine, ...,workflow-you-workflow-name git repos which track versions of workflows on the PhenoMeNal GitHub org (what is your opinion on this @sneumann). What do you think?