Adding non-functional but styled static login page
add LoginHandlerServlet which provides the static HTML for the login page

also do some cleanup in the SearchUI.checkCitation code
redirect to real homepage after login attempt and also store the error message in the session
actually use the new login page
do not show the "you can log in to see more corpora" message by default
open native window instead of redirect, this does not completly work since we don't have any possibility to communicate when the window was closed yet
Merged 'develop'.
using the new push mechanism to update the gui when the login was sucessful
don't crash when the Helper.setUser function is called with a null argument
make the "Cancel" link work
refactored the login process in order to allow the browsers to remember the password