[welcome] Shuffle signals to conventional location

- signals after slots, before private
- while here give the *MessageChanged signals a parameter (the changed
  message)

src/modules/welcome/Config.cpp

@@ -42,7 +42,7 @@ void
 Config::retranslate()
 {
     m_genericWelcomeMessage = genericWelcomeMessage().arg( *Calamares::Branding::VersionedName );
-    emit genericWelcomeMessageChanged();
+    emit genericWelcomeMessageChanged( m_genericWelcomeMessage );
 
     if ( !m_requirementsModel->satisfiedRequirements() )
     {
@@ -81,7 +81,7 @@ Config::retranslate()
                                .arg( *Calamares::Branding::ProductName );
     }
 
-    emit warningMessageChanged();
+    emit warningMessageChanged( m_warningMessage );
 }
 
 CalamaresUtils::Locale::LabelModel*

src/modules/welcome/Config.h

@@ -78,6 +78,19 @@ public slots:
     void retranslate();
     QString languageIcon() const;
 
+signals:
+    void countryCodeChanged( QString countryCode );
+    void localeIndexChanged( int localeIndex );
+    void isNextEnabledChanged( bool isNextEnabled );
+
+    void genericWelcomeMessageChanged( QString message );
+    void warningMessageChanged( QString message );
+
+    void supportUrlChanged();
+    void knownIssuesUrlChanged();
+    void releaseNotesUrlChanged();
+    void donateUrlChanged();
+
 private:
     void initLanguages();
     QVariantMap m_configurationMap;
@@ -95,19 +108,6 @@ private:
     QString m_knownIssuesUrl;
     QString m_releaseNotesUrl;
     QString m_donateUrl;
-
-signals:
-    void countryCodeChanged( QString countryCode );
-    void localeIndexChanged( int localeIndex );
-    void isNextEnabledChanged( bool isNextEnabled );
-
-    void genericWelcomeMessageChanged();
-    void warningMessageChanged();
-
-    void supportUrlChanged();
-    void knownIssuesUrlChanged();
-    void releaseNotesUrlChanged();
-    void donateUrlChanged();
 };
 
 #endif