Merge pull request #345 from pleary/master

Fixed bug with guides with NULL medium_urls
Bugfix: captive col on obs was only getting set by observer (#344)
Minor bugfixes, including #339
Added copyright infringement flags for photos.

Adding this flag changes the URLs for the photo so the content won't
display. It does not delete the photo, and the photo can be restored
by resolving or deleting the flag.
Bugfixes, including #347
Bugfix: projects/show was broken when viewing projects you hadn't joined.