Fix #20:

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

include/gds-render/cell-selector/tree-store.h

@@ -0,0 +1,57 @@
+/*
+ * 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 tree-store.h
+ * @brief Header file for Tree store implementation
+ * @author Mario Hüttel <mario.huettel@gmx.net>
+ */
+
+/**
+ * @addtogroup GUI
+ * @{
+ */
+
+#ifndef __TREE_STORE_H__
+#define __TREE_STORE_H__
+
+#include <gtk/gtk.h>
+
+/** @brief Columns of selection tree view */
+enum cell_store_columns {
+        CELL_SEL_LIBRARY = 0,
+        CELL_SEL_CELL,
+	CELL_SEL_CELL_ERROR_STATE, /**< Used for cell color and selectability */
+        CELL_SEL_MODDATE,
+        CELL_SEL_ACCESSDATE,
+	CELL_SEL_COLUMN_COUNT /**< @brief Not a column. Used to determine count of columns */
+};
+
+struct tree_stores {
+		GtkTreeView *base_tree_view;
+		GtkTreeStore *base_store;
+		GtkTreeModelFilter *filter;
+		GtkEntry *search_entry;
+};
+
+struct tree_stores *setup_cell_selector(GtkTreeView* view, GtkEntry *search_entry);
+
+#endif /* __TREE_STORE_H__ */
+
+/** @} */