Contingency lists improvements

[etiennehomer]

• Do you want to request a feature or report a bug?
  Bug/improvements required for GridSuite's needs on identifiers based contingency lists.

• What is the current behavior?

1/ we have a useless field identifiableType in IdentifierContingencyList

Expected behavior :
done in #2491

2/ there's no 'name' field on NetworkElementIdentifierList class.

Expected behavior :
We'd like to associate a name to each NetworkElementIdentifierList.
#2515

3/ we can create N-K defaults but the k defaults are not applied, only the first one is used in filterIdentifiable(). only N-1 defaults are supported
done in #2515

Expected behavior :
We'd like to create and filter with N-K default lists.

4/ ContingencyList type is a simple String

Expected behavior : we could use an enum but it's not a priority
not required

5/ GroovyContingencyList is not serializable because of fied GroovyCodeSource codeSource. It makes impossible the mapping with this class in GridSuite. Do we want to change the design of GroovyContingencyList ? We keep it like this and GS will not be homogeneous on this class ?
Expected behavior : not required actually

6/ There is only one nominal voltage for LineCriterionContingencyList.

Expected behavior :
We'd like to use a DoubleNominalVoltageCriterion

7/ When the list of countries of SingleCountryCriterion is empty, no contingency is returned.
#2512 (closed PR)
done in #2515

8/ 2 nominal voltage criterions for HvdcLines. Should be one ?

• What is the motivation / use case for changing the behavior?
  These changes are needed for GridSuite integration of contingency lists.