Ability to add text before username field in login page

I often need to add some lengthy directions on the logon form and they don't work well in a block before the user form. And they are usually too long for the user field directions. The attached patch adds another variable username_inpage_prefix to the module and if set displays it above the user field.

Love this module. I have to tweak the user form all the time and want to be able to do it independent of themes and allow site admins to make changes; so this is the perfect fix for me. I especially like that its scope is very reasonable.