Increase request timeout of the configuration web UI

[mariusoe]

Currently, the timeout for each request made by the configuration server's web UI is at 5 seconds. This is quite optimistic and leads often to timeouts in case the configuration server is not that fast.

In order to ensure requests can be succesfully be loaded, even the server is slower than usual, the timeout should be increase, e.g. to 15 seconds. By doing this, users are able to continue to work even when using a slow server.