Added remote_user to plays

Still compatible with user: but deprecating it so we can have
a matching remote_user: in tasks, cannot be user: because of the
module of the same name. #3932

Signed-off-by: Brian Coca <briancoca+dev@gmail.com>
fixed typo
Signed-off-by: Brian Coca <briancoca+dev@gmail.com>
Merge branch 'play_remote_user' of https://github.com/bcoca/ansible into bcoca-play_remote_user
Adding a note in the documentation regarding user->remote_user change