Core: New and themable locked/unlocked icon

This change replaces the existing locked/unlocked icons with Diana's
icons and makes them themable. Now, they fit much better into the UI.
Especially in the dark theme.

Change-Id: I51beb3be202af8f2f467e81701cd5f27a6837d1c
Reviewed-by: Alessandro Portale <alessandro.portale@theqtcompany.com>

src/plugins/coreplugin/core.qrc

@@ -24,6 +24,8 @@
         <file>images/linkicon@2x.png</file>
         <file>images/locked.png</file>
         <file>images/locked@2x.png</file>
+        <file>images/lockedbackground.png</file>
+        <file>images/lockedbackground@2x.png</file>
         <file>images/magnifier.png</file>
         <file>images/magnifier@2x.png</file>
         <file>images/minus.png</file>

src/plugins/coreplugin/coreicons.cpp

@@ -52,10 +52,11 @@ const Icon RESET(
         QLatin1String(":/core/images/reset.png"));
 const Icon DARK_CLOSE(
         QLatin1String(":/core/images/darkclose.png"));
-const Icon LOCKED(
-        QLatin1String(":/core/images/locked.png"));
-const Icon UNLOCKED(
-        QLatin1String(":/core/images/unlocked.png"));
+const Icon LOCKED({
+        {QLatin1String(":/core/images/lockedbackground.png"), Theme::PanelStatusBarBackgroundColor},
+        {QLatin1String(":/core/images/locked.png"), Theme::IconsBaseColor}}, Icon::Tint);
+const Icon UNLOCKED({
+        {QLatin1String(":/core/images/unlocked.png"), Theme::IconsDisabledColor}}, Icon::Tint);
 const Icon FIND_CASE_INSENSITIVELY(
         QLatin1String(":/find/images/casesensitively.png"));
 const Icon FIND_WHOLE_WORD(