Fully rename Twitter to "Social Media"

Fully rename Twitter to "Social Media"

Commit 6cad91e just renamed the button on the admin page but failed to change
it throughout the entire codebase. This commit also changes the name in the
documentation as well as on the model, this fixing the entire system.

One thing that this does *not* do is rename the actual code as that seems like
too much of an invasive change.