Fix #20:

Move all cell selector specific code to a new folder "cell-selector".

include/gds-render/cell-selector/lib-cell-renderer.h

@@ -0,0 +1,70 @@
+/*
+ * GDSII-Converter
+ * Copyright (C) 2018  Mario Hüttel <mario.huettel@gmx.net>
+ *
+ * This file is part of GDSII-Converter.
+ *
+ * GDSII-Converter is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * GDSII-Converter is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GDSII-Converter.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/**
+ * @file lib-cell-renderer.h
+ * @brief Header file for the LibCellRenderer GObject Class
+ * @author Mario Hüttel <mario.huettel@gmx.net>
+ */
+
+/**
+ * @addtogroup LibCellRenderer
+ * @{
+ */
+
+#ifndef __LIB_CELL_RENDERER_H__
+#define __LIB_CELL_RENDERER_H__
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+G_DECLARE_FINAL_TYPE(LibCellRenderer, lib_cell_renderer, LIB_CELL, RENDERER, GtkCellRendererText)
+#define TYPE_LIB_CELL_RENDERER (lib_cell_renderer_get_type())
+
+/** @{
+ * Error levels
+ */
+#define LIB_CELL_RENDERER_ERROR_WARN (1U<<0)
+#define LIB_CELL_RENDERER_ERROR_ERR (1U<<1)
+/** @} */
+
+typedef struct _LibCellRenderer {
+        /* Inheritance */
+        GtkCellRendererText super;
+        /* Custom Elements */
+} LibCellRenderer;
+
+/**
+ * @brief lib_cell_renderer_get_type
+ * @return GObject Type
+ */
+GType lib_cell_renderer_get_type(void);
+
+/**
+ * @brief Create a new renderer for renderering @ref gds_cell and @ref gds_library elements.
+ * @return New renderer object
+ */
+GtkCellRenderer *lib_cell_renderer_new(void);
+
+G_END_DECLS
+
+#endif /* __LIB_CELL_RENDERER_H__ */
+
+/** @} */