Entering an asterisk as host can create confusion

[Sebobo]

When entering an asterisk the result will be that the created redirect will not work as it will never match a normal host.

This is not such a big issue, but the problem is impossible to see in the redirect list as we render an asterisk when the host field is empty. Therefore both variants look the same but behave differently.

This could also be solved together with #18. At some point we need a good regex for validating the host field too.