Add LoginPanel to the WMT header panel
Start setting up LoginPanel

I'm modifying AuthenticationHandler to do so. LoginHandler is
deprecated.
Show username in LoginPanel when logged in

This mimics the behavior of the Eric's API login at
http://csdms.colorado.edu/wmt/api-dev/.

When logged out, revert to showing the email and password TextBoxes.
Give sign in button focus on tab

This fixes the problem where a user could tab from the email box to the
password box, but not to the sign in button.
Hook up the LoginPanel to the API login system

Still need to authenticate login and throw error on incorrect or null
login.