The rationale behind this is that if the user wants to report violent media,
they might not want to see it repeatedly. The “sensitive” property is still
kept, displaying different messages for hidden media depending on whether
they are marked as sensitive.

Port the display part of the following commits to glitch-soc:
* 90f12f2e5a
* b170627ceb
* 11697d6894
* 56eb5c3f34

Port the video-player part of 036dd98abb to
glitch-soc. MediaGallery part ignored since it has diverged quite a bit.

This fixes #423

Port ecdac9017e to glitch-soc

Port the UI part of 76f3d5d16b to glitch-soc