Small fix for mail template style on very small screens
Change old ajax endpoint to the new one

The new endpoint for ajax is `/backend/ajax`. This file still used the old one.
Bugfix right aligned tabs

In previous versions of Fork, the less important tabs were aligned on to the right side. The body element of the page was in 3.6.6: `body#pages.pagesAddEdit`.
This is now (apparently) divided into: `body#pages.pagesAdd`(if you add a page) and `body#pages.pagesEdit` (if you edit an existing page).

So the CSS rules needed to change to these two classes instead of one.

This commit fixes #766
Merge pull request #847 from jessedobbelaere/fix-backend.js-ajax-endpoint

Change old ajax endpoint to the new one
Update AddCategory.php

Craches because could not find specified file :)
Merge pull request #866 from vytenizs/patch-1

Update AddCategory.php
Merge pull request #846 from bart-lysander/RestyledMailTemplates2

Small fix for mail template style on very small screens
Merge pull request #848 from jessedobbelaere/bugfix-pages-rightaligned-tabs

Bugfix right aligned tabs