Added text and password widget HTML5 attributes required by plone.login.

Eric, as discussed at Emerald Sprint, these are the minimal changes to z3c.form required for plone.login. I have added complete test converage for these changes. If you would please roll this release, then we could revise the plone.login buildout to pull it. If you would do that, then I would commit to the much lengthier work of revising z3c.form for all new HTML5 attributes.