Revision 2023

Documentation synced with 1.0rc1

* Doc/manual/thuban-manual.xml:
	Minor formatting changes and references to database layers .
	Introduction.Internationalization: New section on i18n.
	MapManagement.AddingandRemovingLayers: Added item on database layers.
	MapManagement.TheLegend: Added section and screenshot on popup menu.
	ProjectionManagement: Updated screenshot and sentence on EPSG.
	Appendix.SupportedDataSources: Added PostGIS.
	Appendix.WorkingwithPostGIS: New section.

* Doc/manual/images/6_projection.png: Updated screenshot including
	EPSG checkboxes.

* Doc/manual/images/3_5_popup_menu.png: New, popup menu screenshot.

* Doc/manual/images/app_postgis_add_layer.png,
	Doc/manual/images/app_postgis_db_add.png,
	Doc/manual/images/app_postgis_db_management.png:
	New screenshots focussing on database layers