Integrated Gallery into DataCultures: images and videos load properly

https://jira.ets.berkeley.edu/jira/browse/CYB-80

Initial integration of Gallery into DataCultures

Styling will be completely revamped by @ericayin, at the moment only functionality is of core value
@NolanChan mainly just to prefix it, `dc-image` or `dc-gallery` whatever makes most sense to you.