Add loadTapChangingCapabilities attribute on PhaseTapChanger

[miovd]

• Do you want to request a feature or report a bug?
  A feature

• What is the current behavior?
  Phase tap changers do not have loadTapChangingCapabilities attributes.

• What is the expected behavior?
  Phase tap changers should have loadTapChangingCapabilities attributes like ratio tap changers.

• What is the motivation / use case for changing the behavior?
  In CGMES conversion, not having a loadTapChangingCapabilities attribute leads to information loss.

• Please tell us about your environment:

  • PowSyBl Version: 3.0.0-SNAPSHOT

• Other information (e.g. detailed explanation, stacktraces, related issues, suggestions how to fix, links for us to have context, eg. stackoverflow, spectrum, etc)
  This might be done after t3w IIDM refactoring.