Port away from KParts::Plugin

This class got deprecated in KParts.

Task: https://phabricator.kde.org/T13806

libktcore/interfaces/plugin.cpp

@@ -8,9 +8,9 @@
 namespace kt
 {
 Plugin::Plugin(QObject *parent, const KPluginMetaData &data, const QVariantList &args)
-    : KParts::Plugin(parent)
+    : QObject(parent)
 {
-    setMetaData(data);
+    Q_UNUSED(data);
     Q_UNUSED(args)
 }
 

libktcore/interfaces/plugin.h

@@ -32,7 +32,7 @@ class GUIInterface;
  * (setting an int to 0 is ok, creating widgets isn't).
  * Only the name, author and description may be set in the constructor.
  */
-class KTCORE_EXPORT Plugin : public KParts::Plugin
+class KTCORE_EXPORT Plugin : public QObject, public KXMLGUIClient
 {
     Q_OBJECT
 public: