Move press release images to their own folder

lms/static/images/press/releases/cengage_book_327x400.jpg

lms/static/images/press/releases/diploma-109x84.jpg

lms/static/images/press/releases/edx-109x84.png

...ic/images/press/releases/elsevier_page_sample_680x660.png

...ic/images/press/releases/foundations-of-analog-109x84.jpg

.../images/press/releases/tumblr_tumbnail_brazilian_teen.jpg

...press/releases/tumblr_tumbnail_opening_doors_mongolia.jpg

lms/static/images/press/releases/uts-seal_109x84.jpg

lms/templates/feed.rss

...lates/press_releases/Cengage_to_provide_book_content.html

...plates/press_releases/Elsevier_collaborates_with_edX.html