MDL-39305 fixed display bugs in course listings

- When category has a lot of subcategories and courses and user clicks 'view more' for categories, the courses are still displayed
- Course summary non-image files may appear above course summary image files, and they don't have an icon with the filetype
MDL-39297 fixed mistype in tag name label
MDL-38594 page-course-category is replaced with page-course-index because page has moved
MDL-38594 temp