[calamares] Make logging output more consistent

- Use Logger::SubEntry instead of various indents
 - Improve wording of message

src/calamares/CalamaresWindow.cpp

@@ -79,7 +79,7 @@ CalamaresWindow::CalamaresWindow( QWidget* parent )
     int w = qBound( minimumSize.width(), windowDimensionToPixels( brandingSizes.first ), availableSize.width() );
     int h = qBound( minimumSize.height(),  windowDimensionToPixels( brandingSizes.second ), availableSize.height() );
 
-    cDebug() << "  Proposed window size:" << w << h;
+    cDebug() << Logger::SubEntry << "Proposed window size:" << w << h;
     resize( w, h );
 
     QBoxLayout* mainLayout = new QHBoxLayout;

src/calamares/testmain.cpp

@@ -223,7 +223,7 @@ main( int argc, char* argv[] )
         Calamares::JobResult r = p->exec();
         if ( !r )
         {
-            cDebug() << count << ".. failed"
+            cDebug() << "Job #" << count << "failed"
                 << TR( "summary", r.message() )
                 << TR( "details", r.details() );
         }