Make method naming more consistent.

* Use id() for methods returning a string used to represent
    some type of object.
  * Use displayName() for strings that are meant to be user
    visible.
  * Quieten some warnings while touching the files anyway.
  * Move Factories to their products in the plugins where that
    was not done before.

Reviewed-by: dt

src/plugins/cpptools/completionsettingspage.cpp

@@ -55,7 +55,7 @@ QString CompletionSettingsPage::id() const
     return QLatin1String("P.Completion");
 }
 
-QString CompletionSettingsPage::trName() const
+QString CompletionSettingsPage::displayName() const
 {
     return tr("Completion");
 }
@@ -65,7 +65,7 @@ QString CompletionSettingsPage::category() const
     return QLatin1String(TextEditor::Constants::TEXT_EDITOR_SETTINGS_CATEGORY);
 }
 
-QString CompletionSettingsPage::trCategory() const
+QString CompletionSettingsPage::displayCategory() const
 {
     return QCoreApplication::translate("Text Editor", TextEditor::Constants::TEXT_EDITOR_SETTINGS_TR_CATEGORY);
 }