ui: basic search view

- Added a basic SearchView (+ controller and qt implementation)
- SearchView can set the active element of other views by dispatching a message.
- SearchView adjusts its text when the active element is changed by other views.
- Added wrappers for Button and EditBox that allow the usage of simple callback functions.

src/app/qt/element/QtEditBox.cpp

@@ -0,0 +1,23 @@
+#include "qt/element/QtEditBox.h"
+
+QtEditBox::QtEditBox(QWidget *parent)
+	: QLineEdit(parent)
+	, m_onReturnPressed(nullptr)
+{
+	connect(this, SIGNAL(returnPressed()), this, SLOT(slotOnReturnPressed()));
+}
+
+QtEditBox::~QtEditBox()
+{
+}
+
+void QtEditBox::setCallbackOnReturnPressed(std::function<void(void)> callback)
+{
+	m_onReturnPressed = callback;
+}
+
+void QtEditBox::slotOnReturnPressed()
+{
+	if (m_onReturnPressed)
+		m_onReturnPressed();
+}