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 'same_as' in schema:
sync_schema_props_perms('same_as', syncperms=False)
sync_schema_props_perms('Bookmark', syncperms=False)