[packagechooser] Add configuration setting for selection mode

- Add a *mode* key to the configuration file
 - Change some names around to be more consistent (not user-visible)

src/modules/packagechooser/PackageChooserViewStep.cpp

@@ -150,6 +150,16 @@ void
 PackageChooserViewStep::setConfigurationMap( const QVariantMap& configurationMap )
 {
     // TODO: use the configurationMap
+    QString mode = CalamaresUtils::getString( configurationMap, "mode" );
+    bool ok = false;
+    if ( !mode.isEmpty() )
+    {
+        m_mode = roleNames().find( mode, ok );
+    }
+    if ( !ok )
+    {
+        m_mode = PackageChooserMode::Required;
+    }
 
     if ( !m_model )
     {

src/modules/packagechooser/PackageModel.cpp

@@ -25,17 +25,16 @@ roleNames()
 {
     static const NamedEnumTable< PackageChooserMode > names {
         { "optional", PackageChooserMode::Optional },
-        { "exclusive", PackageChooserMode::Exclusive },
-        { "multiple", PackageChooserMode::Multiple },
-        { "requiredmultiple",
-        PackageChooserMode::RequiredMultiple },
+        { "required", PackageChooserMode::Required },
+        { "optionalmultiple", PackageChooserMode::OptionalMultiple },
+        { "requiredmultiple", PackageChooserMode::RequiredMultiple },
         // and a bunch of aliases
         { "zero-or-one", PackageChooserMode::Optional },
-        { "radio", PackageChooserMode::Exclusive },
-        { "one", PackageChooserMode::Exclusive },
-        { "set", PackageChooserMode::Multiple },
-        { "zero-or-more", PackageChooserMode::Multiple },
-        { "required", PackageChooserMode::RequiredMultiple },
+        { "radio", PackageChooserMode::Required },
+        { "one", PackageChooserMode::Required },
+        { "set", PackageChooserMode::OptionalMultiple },
+        { "zero-or-more", PackageChooserMode::OptionalMultiple },
+        { "multiple", PackageChooserMode::RequiredMultiple },
         { "one-or-more", PackageChooserMode::RequiredMultiple } };
     return names;
 }

src/modules/packagechooser/PackageModel.h

@@ -29,8 +29,8 @@
 enum class PackageChooserMode
 {
     Optional,  // zero or one
-    Exclusive,  // exactly one
-    Multiple,  // zero or more
+    Required,  // exactly one
+    OptionalMultiple,  // zero or more
     RequiredMultiple  // one or more
 };
 

src/modules/packagechooser/packagechooser.conf

@@ -0,0 +1,9 @@
+# Configuration for the low-density software chooser
+---
+# Software selection mode, to set whether the software packages
+# can be chosen singly, or multiply.
+#
+# Possible modes are "optional", "required" (for zero or one)
+# or "optionalmultiple", "requiredmultiple" (for zero-or-more
+# or one-or-more).
+mode: required