[packagechooser] Implement AppData loading

- An item can refer to *appdata* and load that, or provide
   the data in the config file itself.
 - Fix documentation about translations.

src/modules/packagechooser/PackageChooserViewStep.cpp

@@ -232,7 +232,14 @@ PackageChooserViewStep::fillModel( const QVariantList& items )
             continue;
         }
 
-        m_model->addPackage( PackageItem( item_map ) );
+        if ( item_map.contains( "appdata" ) )
+        {
+            m_model->addPackage( PackageItem::fromAppData( CalamaresUtils::getString( item_map, "appdata" ) ) );
+        }
+        else
+        {
+            m_model->addPackage( PackageItem( item_map ) );
+        }
     }
 }
 

src/modules/packagechooser/packagechooser.conf

@@ -24,8 +24,11 @@ mode: required
 # pretty short list to avoid overwhelming the UI. This is a list
 # of objects, and the items are displayed in list order.
 #
-# Each item has an id, which is used in setting # the value of 
+# Either provide the data for an item in the list (using the keys
-# *packagechooser_<module-id>*). The following fields
+# below), or use existing AppData XML files as a source for the data.
+#
+# For data provided by the list: the item has an id, which is used in 
+# setting the value of *packagechooser_<module-id>*). The following fields
 # are mandatory:
 #
 #  - *id* ID for the product. The ID "" is special, and is used for
@@ -33,13 +36,24 @@ mode: required
 #    selecting none.
 #  - *package* Package name for the product. While mandatory, this is
 #       not actually used anywhere.
-#  - *name* Human-readable, but untranslated, name of the product.
+#  - *name* Human-readable name of the product. To provide translations,
-#  - *description* Human-readable, but untranslated, description.
+#       add a *[lang]* decoration as part of the key name, e.g. `name[nl]`
+#       for Dutch. The list of usable languages can be found in
+#       `CMakeLists.txt` or as part of the debug output of Calamares.
+#  - *description* Human-readable description. These can be translated
+#       as well.
 #  - *screenshot* Path to a single screenshot of the product. May be
 #       a filesystem path or a QRC path (e.g. ":/images/no-selection.png").
 #
 # Use the empty string "" as ID / key for the "no selection" item if
 # you want to customize the display of that item as well.
+#
+# For data provided by AppData XML: the item has an *appdata*
+# key which points to an AppData XML file in the local filesystem.
+# This file is parsed to provide the id (from AppData id), name
+# (from AppData name), description (from AppData description paragraphs
+# or the summary entries), and a screenshot (the defautl screenshot
+# from AppData). No package is set (but that is unused anyway).
 items:
     - id: ""
       package: ""
@@ -58,5 +72,5 @@ items:
       name: GNOME
       description: GNU Networked Object Modeling Environment Desktop
       screenshot: ":/images/gnome.png"
-
+    - appdata: ../io.calamares.calamares.appdata.xml