run with runDate -> runTime

[mbaudis]

• allows more finegrained annotation
• removed requirement, since frequently not available

[mbaudis]

@jrambla

• required: shouldn't be used for "housekeeping purposes"; the parameter isn't strictly necessary and in fact will not be available in many instances, especially when converting existing data (i.e. we don't have this available for most samples). So making this a requirement should be done on implementer side, not in the schema.
• date-time instead of date: This is the correct format.
• runTime instead of runDate: Finer granularity is more sensible, and the correct AFAIK date-time format allows both anyway. Now, the renaming would be cosmetic (but informative)...

So to keep things stable for now I've reverted the parameter name change & just kept the changed format & description. O.k.?

[jrambla]

I will merge that as it seems to me that changes we are introducing are retrocompatible. I'm still having some doubts on the "required" as we did that in purpose, but lets allow the community talk when this thing is out ;-)