Added an AbstractDialog class and using it as base for a NewItemDialog class (no new item functionality yet).

Dialogs/newitemdialog.h

@@ -0,0 +1,32 @@
+#ifndef NEWITEMDIALOG_H
+#define NEWITEMDIALOG_H
+
+#include "abstractdialog.h"
+
+class QLineEdit;
+class QSpinBox;
+class QLabel;
+class NewItemDialog : public AbstractDialog {
+ public:
+  NewItemDialog(QWidget* parent = nullptr);
+
+  void createContent() override;
+
+ private:
+  QLabel* m_nameLabel   = nullptr;
+  QLineEdit* m_nameEdit = nullptr;
+
+  QLabel* m_descriptionLabel   = nullptr;
+  QLineEdit* m_descriptionEdit = nullptr;
+
+  QLabel* m_infoLabel   = nullptr;
+  QLineEdit* m_infoEdit = nullptr;
+
+  QLabel* m_amountLabel = nullptr;
+  QSpinBox* m_amountBox = nullptr;
+
+  QLabel* m_factorLabel = nullptr;
+  QSpinBox* m_factorBox = nullptr;
+};
+
+#endif  // NEWITEMDIALOG_H