Fake password autofill

Stop administrator user password to be filled when editing a user.

Prevent browsers autofill username and password where they should not, just by adding a "fake" fields in the beginning of the form as discussed here:

https://groups.google.com/forum/#!topic/joomla-dev-cms/yGIHq7g__uU

This PR is related with this other that I have also submitted:

https://github.com/joomla/joomla-cms/pull/4952

All forms with password fields should be faked like this as modern browsers are not going to provide a different way to prevent autofill as discussed.

Regards