Support properly HTML5 implicit form submission.

From Chromium 31, pressing enter key to select ListBox page submit the form
through JS (submitFormOnEnter) *and* wrongly on the default button, at the end
following HTML5 behavior (4.10.22.2 Implicit submission).

Conflicts:
	product/ERP5/bootstrap/erp5_xhtml_style/bt/change_log
	product/ERP5/bootstrap/erp5_xhtml_style/bt/revision