libgimp: rename gimpmetadata.[ch] to gimpimagemetadata.[ch]

so the filenames match the contained namespace. Sort includes in
gimpui.h alphabetically.

libgimp/gimpimagemetadata.h

@@ -0,0 +1,61 @@
+/* LIBGIMP - The GIMP Library
+ * Copyright (C) 1995-2000 Peter Mattis and Spencer Kimball
+ *
+ * gimpimagemetadata.h
+ *
+ * This library is free software: you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 3 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ */
+
+#if !defined (__GIMP_UI_H_INSIDE__) && !defined (GIMP_COMPILATION)
+#error "Only <libgimp/gimpui.h> can be included directly."
+#endif
+
+#ifndef __GIMP_IMAGE_METADATA_H__
+#define __GIMP_IMAGE_METADATA_H__
+
+G_BEGIN_DECLS
+
+/* For information look into the C source or the html documentation */
+
+
+GimpMetadata * gimp_image_metadata_load_prepare (gint32                 image_ID,
+                                                 const gchar           *mime_type,
+                                                 GFile                 *file,
+                                                 GError               **error);
+void           gimp_image_metadata_load_finish  (gint32                 image_ID,
+                                                 const gchar           *mime_type,
+                                                 GimpMetadata          *metadata,
+                                                 GimpMetadataLoadFlags  flags,
+                                                 gboolean               interactive);
+
+GimpMetadata * gimp_image_metadata_save_prepare (gint32                 image_ID,
+                                                 const gchar           *mime_type,
+                                                 GimpMetadataSaveFlags *suggested_flags);
+gboolean       gimp_image_metadata_save_finish  (gint32                 image_ID,
+                                                 const gchar           *mime_type,
+                                                 GimpMetadata          *metadata,
+                                                 GimpMetadataSaveFlags  flags,
+                                                 GFile                 *file,
+                                                 GError               **error);
+
+
+/* this is experimental API, to be finished for 2.10 */
+
+gint32       gimp_image_metadata_load_thumbnail (GFile                 *file,
+                                                 GError               **error);
+
+G_END_DECLS
+
+#endif /* __GIMP_IMAGE_METADATA_H__ */