Minor changes

Space deletion. Fix minor doc on translator constant.
Replaced services.xml with services.yml
Twig extension update

Added a doc for manager, for useful autocomplete.
Constructor only adds service container to the class.
Replaced static attributes, set to instanciated attributes only. Saves
memory, and was not useful in the end.
Renamed everything with "route" by "domain", as it's more relevant to
speak about `translation domains`. Aliases are still in use for
compatibility.
The domain can be specified in the twig filter, for momentary
translation.
If the domain is not specified, it first looks at the route name. If the
translator is not called by a browser, then it's command line, so it
affects default translation domains.
Translator update

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