Improved map configuration window

The following changes have been made to the map configuration window:

• The options available in the configuration window for maps from WMS services can now be obtained from the description of the service itself. This is done via the "GetCapabilities" request defined in the OpenGIS specification for WMS.
• The sources are located in the left sidebar of the window and organised in a tree. This makes it easier to identify the WMS services associated with each country.
• In the UTM coordinate selection of the WMS services, all reference systems are displayed in EPSG code.
• The layers available in the WMS services are now displayed in a tree structure according to the service description. They also include the "Description", "Attribution" and "Styles" columns.