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.

include *.py
include */*.py
recursive-include data *.gif *.png *.ico *.css *.js
recursive-include i18n *.po
recursive-include wdoc *