Define BASE_URL and DATA_URL js variables in the login template. Closes #13385185 Those are expected to be defined in almost every js files. They were not before this patch because login form doesn't use the regular main template.

if not rql('CWConstraintType X WHERE X name "RQLUniqueConstraint"',
           ask_confirm=False):
    rql('INSERT CWConstraintType X: X name "RQLUniqueConstraint"',
        ask_confirm=False)