calamares: sidebarTextHighlight for branding

This commit adds support for distribution to define sidebarTextHighlight to their
branding.desc file, to control the left panel (sidebar) with highlight behind the
current step (isCurrent) text label.

src/calamares/progresstree/ProgressTreeDelegate.cpp

@@ -104,7 +104,8 @@ ProgressTreeDelegate::paintViewStep( QPainter* painter,
     {
         painter->setPen( Calamares::Branding::instance()->
                          styleString( Calamares::Branding::SidebarTextSelect ) );
-        painter->setBrush( APP->mainWindow()->palette().background() );
+        painter->setBrush( QColor( Calamares::Branding::instance()->
+                           styleString( Calamares::Branding::SidebarTextHighlight ) ) );
     }
 
     painter->fillRect( option.rect, painter->brush().color() );

src/libcalamaresui/Branding.cpp

@@ -71,7 +71,8 @@ QStringList Branding::s_styleEntryStrings =
 {
     "sidebarBackground",
     "sidebarText",
-    "sidebarTextSelect"
+    "sidebarTextSelect",
+    "sidebarTextHighlight"
 };
 
 

src/libcalamaresui/Branding.h

@@ -62,7 +62,8 @@ public:
     {
         SidebarBackground,
         SidebarText,
-        SidebarTextSelect
+        SidebarTextSelect,
+        SidebarTextHighlight
     };
 
     static Branding* instance();