Should be able to specify titles on a per-activity type basis

[irace]

The more I think about this, the more I think we would actually want to be able to key titles off of activity types, if we’re going to use them as the subject that the UIActivityItemSource provides. I realized this by sharing from the Tumblr app to the Tumblr extension and realizing that our subjects written specifically for email don’t translate well to quote posts or link posts, where we consume the title field in our extension.