Add vue component for confirmation popover

Have the confirmation popover in a separate Vue component fixes a bug in
IE that was causing the `form` element in the popover to be ignored.

Since `form`s cannot be nested, the `form` element in the popover was
being discarded by IE and the revoke/resend invitation buttons did
nothing.

Breaking the functionality into a Vue component moves the `form` into a
separate template. When the popover is displayed, the component is added
to the DOM at the end, so the `form` is properly not-nested.

templates/workspaces/members/edit.html

@@ -44,14 +44,12 @@
         {{ ConfirmationButton(
               "Revoke Invitation",
               url_for("workspaces.revoke_invitation", workspace_id=workspace.id, token=member.latest_invitation.token),
-              form.csrf_token
            ) }}
       {% endif %}
       {% if member.can_resend_invitation %}
         {{ ConfirmationButton (
               "Resend Invitation",
               url_for("workspaces.resend_invitation", workspace_id=workspace.id, token=member.latest_invitation.token),
-              form.csrf_token,
               confirm_msg="Are you sure? This will send an email to invite the user to join this workspace."
         )}}
       {% endif %}