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/resourceeditor/resourceeditorw.cpp

@@ -157,8 +157,8 @@ bool ResourceEditorFile::save(const QString &name /*= QString()*/)
     return true;
 }
 
-const char *ResourceEditorW::kind() const {
-    return ResourceEditor::Constants::C_RESOURCEEDITOR;
+QString ResourceEditorW::id() const {
+    return QLatin1String(ResourceEditor::Constants::C_RESOURCEEDITOR_ID);
 }
 
 QString ResourceEditorFile::fileName() const