[Nexus] Correct way to specify multiple signals

[V. Armando Sole]

Dear colleagues,

It has been a difficult week and I am still working on it, but you can 
download a tentative example (still needs improvements) for one of the 
acquisition use cases I foresee (the link will expire at the end of the 
month):

https://cloud.esrf.fr/index.php/s/N4zbr1dzCDDKbWg

As I said, one of our objectives is that the end user can recover as 
default plot the plot shown during the acquisition. For those using 
SPEC, the idea is to be able to map the plotselect to the NeXus file.

Those scans correspond to energy scans with a multielement detector and 
the goal is to visualize the contents of all the Ni Ka ROIs 
corresponding to what the user was interested on during the experiment.
The intention is to have the signal in the NXdata group corresponding to 
the central element and the auxiliary_signals to the rest of elements.

As I said, it is still a work in progress but I hope you get the idea. 
Hopefully next week I can provide example and viewer.

See you,

Armando