Atto plugin steals default submit action so enter key in other fields no longer submits the form

In Atto, button groups are using a button without a type attribute. They should delcare the type button.

When focused on an input element, hitting the Enter key should trigger the form's submit button, or the closest button of type submit. However, when a button not declaring its type is found before a submit one, it will be given precedence.

 Replication steps

• Create a new Page activity, and save.
• Go back to the Page setting, and focus the "Name" field
• Hit the "Enter" key

Expected

• The form is submitted

Actual

• Atto's "Title" plugin is given the focus and its dropdown opens

(Tested in laster master with Firefox)