Improve multi domain situation

[mirodietiker]

Both redirects and 404s have problems with an environment that involves multiple domains.

By default, Drupal ignores the domain mostly and just considers the routes. Except for per-language domains... Then we have aliases that are limited to a language only.
The log is now already language aware.

When releasing a site that previously had multiple domains, then redirects possibly want to be limited to a specific domain.

The idea is to add an optional domain field per redirect (needs consideration in the hash, much work...).
And 404s should be clearly identifyable, so a fix404 is properly prefilled with the domain.

A redirect might want to target to a different domain. This needs investigation.
There are many potential problems such as entities that change language on update and generate redirects. Also the combination with the recent recursive resolution of redirects needs investigation.

[mirodietiker]

Much related to #53