Implemented the host name auto suggestion, and added Preset feature

ui/xhr.js

@@ -15,7 +15,7 @@
 // You should have received a copy of the GNU Affero General Public License
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-export function head(url, headers) {
+export function get(url, headers) {
   return new Promise((res, rej) => {
     let authReq = new XMLHttpRequest();
 
@@ -35,7 +35,7 @@ export function head(url, headers) {
       rej(e);
     };
 
-    authReq.open("HEAD", url, true);
+    authReq.open("GET", url, true);
 
     for (let h in headers) {
       authReq.setRequestHeader(h, headers[h]);