SEO-Features not working properly with umlauts

[phorward]

There are several problems with SEO-URLs managed by VIUR3.
It doesn't seem to work with umlauts and spaces properly.

E.g. it's unclear what the correct URL for "Speicherbräu Bier" will be. It is saved as something like "speicherbräu bier", but the browser will request "speicherbr%C3%A4%40bier" which doesn't match the database entry properly. It first seemed to be a case-sensitivity problem as fixed by #801 but this is only a part of the problem.

There is further investigation required on this issue.

[phorward]

I would like to resolve this together with PR #800, therefore the bug will be fixed with viur-core==3.5