Add a name property to OperationalLimitsGroup

[rcourtier]

Describe the current behavior

Following #3139, at CGMES import the IIDM OperationalLimitsGroup id is copied from CGMES OperationalLimitSet rdfid. This is neccesary to ensure a strict 1:1 mapping, as well as be able to match limit values update in SSH with limit creation in EQ.
This has however some limitations:

• The rdfid is not human readable, which makes it possible but not easy to later on select the active set.
• The limit set name is stored as a property of the identifiable holding the limits. That way the name can be retrieved during CGMES export but it's not directly accessible in the IIDM OperationalLimitsGroup, which makes it cumbersome to manipulate OperationalLimitsGroup in IIDM.

Describe the expected behavior

Add a new property: "name" to IIDM OperationalLimitsGroup, with a setter and a getter.

Optionally, add new methods in the FlowsLimitsHolder interface to support manipulation of OperationalLimitsGroup by name:

• getSelectedOperationalLimitsGroupName
• getOperationalLimitsGroupFromName
• setSelectedOperationalLimitsGroupFromName
• removeOperationalLimitsGroupFromName

Describe the motivation

That change would facilitate the selection of the active set using the name:

Optional<OperationalLimitsGroup> selectedGroup = branch.getOperationalLimitsGroups1().stream().filter(g -> g.getName().equals("WINTER")).findFirst();
selectedGroup.ifPresent(g -> branch.setSelectedOperationalLimitsGroup1(g.getId()));

Or more simply if the new methods have been added:

branch.setSelectedOperationalLimitsGroup1FromName("WINTER");

Extra Information

See #3162 for making the IIDM OperationalLimitsGroup id globally unique.