Added Slider WD and increased image upload limit

In preparation for WordPress training, I realized the sites didn’t have a decent image gallery tool and where constrained by a rather small file size upload limit. While I do not want students to put a lot of large files on the server (such things should be accessed from Google Drive), students can now upload files as large as 10MB. They also have access to the Slider WD menu, which allows the easy creation of image sliders, which are useful as galleries.