We used to use a regular JS `confirm`; this makes the UI consistent
with the rest of Studio.

Instead, we use XModule field default values when creating an empty
XModule. Driven by this use case, we also allow for XModules to be
created in memory without being persisted to the database at all. This
necessitates a change to the Modulestore api, replacing clone_item with
create_draft and save_xmodule.

On Linux, coffeescript refuses to compile unless the `catch` keyword has an error
variable to bind to. On Mac, it works just fine either way. Go figure.

Models are extraneous for something as temporary as a notifaction -- this change
moves all the configuration into the views, and removes the models entirely.

Prevent creation of unnecessary template divs, and rename .single_templates to .single-templates for convention.

Because there are some cases where it's OK to fail, and it's not the user's fault