Don't reload on enter in create folder dialog

Instead submit dialog and create new folder. Also have input
field focused on dialog show.

src/octoprint/static/js/app/viewmodels/files.js

@@ -641,6 +641,15 @@ $(function() {
             });
 
             self.addFolderDialog = $("#add_folder_dialog");
+            self.addFolderDialog.on("shown", function() {
+                $("input", self.addFolderDialog).focus();
+            });
+            $("form", self.addFolderDialog).on("submit", function(e) {
+                e.preventDefault();
+                if (self.enableAddFolder()) {
+                    self.addFolder();
+                }
+            });
 
             //~~ Gcode upload
 

src/octoprint/templates/dialogs/files.jinja2

@@ -5,7 +5,7 @@
     </div>
     <div class="modal-body">
         <p>{{ _('Please specify the name of the folder to create.') }}</p>
-        <form class="form-horizontal">
+        <form class="form-horizontal" action="javascript:void(0)">
             <div class="control-group">
                 <label class="control-label">{{ _('Folder name') }}</label>
                 <div class="controls">