Start on Creating Plugins documentation.

Change-Id: Ic75775473cfb405cee5c53b2dc24144dba51a25c
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@nokia.com>

doc/api/examples/exampleplugin/exampleplugin.h

@@ -0,0 +1,39 @@
+#ifndef EXAMPLE_H
+#define EXAMPLE_H
+
+#include "example_global.h"
+
+#include <extensionsystem/iplugin.h>
+
+//! [namespaces]
+namespace Example {
+namespace Internal {
+//! [namespaces]
+
+//! [base class]
+class ExamplePlugin : public ExtensionSystem::IPlugin
+{
+    Q_OBJECT
+//! [base class]
+
+public:
+    ExamplePlugin();
+    ~ExamplePlugin();
+
+//! [plugin methods]
+    bool initialize(const QStringList &arguments, QString *errorString);
+    void extensionsInitialized();
+    ShutdownFlag aboutToShutdown();
+//! [plugin methods]
+
+//! [slot]
+private slots:
+    void triggerAction();
+//! [slot]
+};
+
+} // namespace Internal
+} // namespace Example
+
+#endif // EXAMPLE_H
+