remove the unknown button in js

When you hit enter while an input in a form is in focus, your browser
finds the first button in the form, and carries out that action. So,
for non-js users, we added a hidden submit button with a value of
"unknown" to reflect that we don't know the intention of the user.

However, with JS enabled, this ambiguity doesn't exist - there's only
submit button and forms to fill in at a time, and non-visible fields
aren't even submitted at all. We can remove the unknown button,
supporting enter as submit properly. If the user is on one of the grey
button states, with no submit, it'll press the first button, and go to
the new template / move to existing folder dialog. That's fine enough.

app/assets/javascripts/templateFolderForm.js

@@ -6,6 +6,10 @@
     this.start = function(templateFolderForm) {
       this.$form = $(templateFolderForm);
 
+      // remove the hidden unknown button - if you've got JS enabled then the action you want to do is implied by
+      // which field is visible.
+      this.$form.find('button[value=unknown]').remove();
+
       this.$stickyBottom = this.$form.find('#sticky_template_forms');
 
       this.$stickyBottom.append(this.nothingSelectedButtons);