Followup to commit 776c2eaa : Various fixes for writing of XMI

umbrello/umldoc.cpp
- In function saveToXMI1 reenable call to UMLListView::saveToXMI1 and
  CodeGenerator::saveToXMI1.

umbrello/uml1model/classifier.cpp
- In function saveToXMI1, avoid writing the <UML:Classifier.feature>
  element if both attList and opList are empty.

umbrello/umlwidgets/associationwidgetrole.{h,cpp}
- At function saveToXMI1 remove argument 'suffix'.

umbrello/umlwidgets/associationwidgetrole.cpp
- In function saveToXMI1 remove writing of attributes index[ab] and
  totalcount[ab].
  Writing of attributes shall not be mixed with writing the subelements
  multiplicityWidget/roleWidget/changeabilityWidget because
  attributes may not follow subelements (in particular, attributes of
  role B may not follow subelements of role A).

umbrello/umlwidgets/associationwidget.cpp
- In function saveToXMI1:
  - Postpone saving of m_nameWidget and m_associationLine until after
    all attributes have been written.
    Reason: Subelements may not precede attributes.
  - Save attributes of m_role[A] and m_role[B].  Reason: Their saving
    has been removed from AssociationWidgetRole::saveToXMI1.

CCBUG: 363582