[CHG] ws doc: set right section against a dark background
[FIX] doc: viewport meta missing
[IMP] ws doc: affix language switcher to page top
[FIX] fields.py: Many2one fields only put valid values in cache
[FIX] web: m2o search facet do no set `default_*` context key for "name_search" values
[FIX] fields.py: in many2one convert_to_cache, value can be int but long as well
[FIX] translate: lang detection fallback actually falls back

For instance, when a context was passed to a method, but no lang was defined in the context, it did not tried to fallback to other places where we could have find the user language.