use Data class

[arun-babu]

Use Data class instead of using other classes.

Data class should take care of all aspects like catalog links and resource server links.

The user should only specify the list of resource ids

[rraks]

That can't be done since catalogue url in your patch isn't the right one.
But going forward we should change the catalogue url to be the same for all cities.
We can merge this patch when they becomes the case.

[arun-babu]

It is going to happen. We are going to have a catalog of catalog at https://catalogue.iudx.org.in

[arun-babu]

Otherwise the current code in pyIUDX looks too complex to use.
Consumers should just give the items they want and should be able to get data.