mailbox: add checkbox for pop3

src/views/email.html

@@ -152,6 +152,12 @@
             </div>
           </div>
 
+          <div class="checkbox">
+            <label>
+              <input type="checkbox" ng-model="mailboxes.edit.enablePop3"> {{ 'email.updateMailboxDialog.enablePop3' | tr }}</input>
+            </label>
+          </div>
+
           <div class="checkbox">
             <label>
               <input type="checkbox" ng-model="mailboxes.edit.active"> {{ 'email.updateMailboxDialog.activeCheckbox' | tr }}</input>