Elastic: Don't replace already-existing id attribute of a nav-tab, small improvements in .file-upload

skins/elastic/styles/widgets/forms.less

@@ -787,11 +787,20 @@ html.touch .popupmenu.form {
     border-radius: .5rem;
     border: .2rem dashed @color-table-border;
 
+    fieldset & {
+        margin: 0;
+    }
+
     // TODO background image
 
     .upload-form {
         text-align: center;
         padding-bottom: 1em;
+
+        a.btn,
+        button {
+            margin-bottom: .25rem;
+        }
     }
 
    .hint {

skins/elastic/ui.js

@@ -792,7 +792,7 @@ function rcube_elastic_ui()
             var tabs = [], nav = $('<ul>').attr({'class': 'nav nav-tabs', role: 'tablist'});
 
             $(this).addClass('tab-content').children('fieldset').each(function(i, fieldset) {
-                var tab, id = 'tab' + idx + '-' + i;
+                var tab, id = fieldset.id || ('tab' + idx + '-' + i);
 
                 $(fieldset).addClass('tab-pane').attr({id: id, role: 'tabpanel'});