Fail fast on misconfigurations

[lkiesow]

I've just spent a day of debugging since the configuration format of Studio changed between Opencast 14 and Opencast 16. While it wouldn't have helped in this specific case (see #1187), it would be great if Studio would publically state the misconfiguration (alert, error on page), instead of silently ignoring/changing the configuration in the background.

If the configuration is invalid, the admin probably tried to change something and that clearly didn't work. Therefor, he needs to know that as soon as possible to intervene and fix the configuration.

Just printing a warning in the development console is insufficient, since that's not something people will usually see.