Add initial support for adding settings.

Adds "Add Setting" button to table, and shows a popup with form
elements for adding a new setting. Does not yet add setting to the db.

webui/source/templates/ajax/admin/add-setting.tpl

@@ -0,0 +1,26 @@
+"page_replacements": {
+
+    "dialogheadertitle": {
+        "content": "Add Setting"
+    },
+    
+    "dialogcontent": {
+        {include file="admin/add-setting.tpl" assign=add_setting_content}
+        "content": {$add_setting_content|json_encode}
+    }
+
+},
+
+"dialog": {
+    "show": true,
+    "buttons": {
+        "type": "okcancel",
+        "actions": {
+            "ok": [
+                "add-setting",
+                "close-dialog"
+            ],
+            "cancel": "close-dialog"
+        }
+    }
+}