Fixes not showing the selected cssname

If the first time you access the index page with a param such as
index.php?cssname=mytemplate, when you logout you want to see the exact
same login screen. Hence you need to add the sesson value for the
cssname.
Fixes issue with template on error page

When there is an error on the app, you need to show the login screen
with the selected template the very first time the login/authentication
screen was accessed.
Merge pull request #43 from UlisesArcidiacono/master

Fixes related to cssname