Add support for defaultZ/defaultT

[sbesson]

As noticed as part of the work on https://github.com/IDR/idr0044-mcdole-tardislightsheet/pull/4, the render plugin YML format does not support the OMERO defaultZ/defaultT values.

For some datasets being able to both retrieve and set these values would be extremely valuable. I assume this might be represented as new top-level keys in the YML/JSON format

[sbesson]

As we might converge towards a version 2 of the YML format (https://github.com/ome/omero-cli-render/pull/15#discussion_r248330683), we might as well use the occasion and decision how we are going to represent these concepts in the YML rendering files.

Immediate options coming to mind are z/defaultz/defaultZ and t/defaultt/defaultT, depending on the compromise between short names, matching the OMERO names and keeping every key lowercase. An example would probably look as follows

---
version: 2
z: 5
t: 1
channels:
  1:
    color: "FF0000"
    label: "Red"
    start: 1
    end: 255
    active: True

/cc @dominikl

[jburel]

It is probably time to go back to the discussion about the url formatting for the web viewer since it is exactly the same thing here i.e. what is the best/efficient way to specify rendering settings. Entries like reverse lut will be needed too. and even taking it a step further see https://github.com/ome/omero-iviewer/issues/219

Let's try to unify so all apps "support" the same configuration

[sbesson]

Definitely :+100 for trying and unify/converge on our way to pass/return rendering settings . Also worth including the JSON representation returned by imgData https://docs.openmicroscopy.org/omero/5.4.9/developers/Web/WebGateway.html#imgdata as part of this discussion.

Practically, note we might need to have these features implemented in the upcoming weeks as some upcoming IDR studies might require setting defaultZ/defaultT. What are the next steps to start this discussion ? Should we start listing all representations across the various components and discuss them one by one?

[jburel]

defaultZ and defaultT won't be a problem to introduce I am thinking more about the rest since it will come. Let's go over the various apps after the storm has passed Already in the configuration we have a mix of rendering settings and channel metadata (label)

[sbesson]

Discussed with @dominikl @francesw and @pwalczysko. As some of the images in idr0050 would benefit from setting defaultZ. @dominikl and myself will be looking at extending the render format to support z/t as additional keys.