Support theming for login logo

refs #10705

application/views/scripts/authentication/login.phtml

@@ -1,9 +1,5 @@
  <div id="login">
-  <div class="logo">
-   <div class="image">
-    <img aria-hidden="true" class="fade-in one" src="<?= $this->baseUrl('img/logo_icinga_big.png'); ?>" alt="<?= $this->translate('The Icinga logo'); ?>" >
-   </div>
-  </div>
+  <div id="login-logo" aria-hidden="true"></div>
   <div class="form" data-base-target="layout">
     <?php if ($requiresSetup): ?>
     <p class="config-note"><?= sprintf(

public/css/icinga/login.less

@@ -13,18 +13,6 @@
     padding: 0;
   }
 
-  .logo {
-    text-align: center;
-  }
-
-  .image {
-    padding-top: 5%;
-    margin-left: auto;
-    margin-right: auto;
-    text-align: center;
-    font-size: 0.9em;
-  }
-
   .errors {
     font-size: 0.9em;
     margin-bottom: 0.5em;
@@ -33,10 +21,6 @@
     padding: 0.5em;
   }
 
-  .image img {
-    width: 355px;
-  }
-
   .form {
     position: absolute;
     font-size: 0.9em;
@@ -162,6 +146,16 @@
   }
 }
 
+#login-logo {
+  background-image: url('../img/logo_icinga_big.png');
+  background-position: center;
+  background-repeat: no-repeat;
+  background-size: contain;
+  height: 177px;
+  margin: 0 auto;
+  width: 355px;
+}
+
 /* make keyframes that tell the start state and the end state of our object */
 @-webkit-keyframes fadeIn { from { opacity:0; } to { opacity:1; } }
 @-moz-keyframes fadeIn { from { opacity:0; } to { opacity:1; } }