EogMetadataSidebar: Try to unclutter and improve the sidebar's look

Based on a design by Allan Day.

Plus adding previous tooltip for the folder label

origin commits:
https://gitlab.gnome.org/GNOME/eog/commit/2e5b065
https://gitlab.gnome.org/GNOME/eog/commit/83bf6c4
https://gitlab.gnome.org/GNOME/eog/commit/c0a51e5

Author: fxri

data/Makefile.am

@@ -34,6 +34,7 @@ EXTRA_DIST = \
 	$(ui_DATA) \
 	eom.css			\
 	eom-ui.xml		\
+	metadata-sidebar.ui	\
 	$(DESKTOP_IN_FILES) \
 	$(appdata_in_files)