LDAP Wizard: introduce configuration status indicator, fixes #5741

Introduces a status bar like indicator about the configuration state. Looks like this:

![indicator](https://f.cloud.github.com/assets/2184312/1500382/c5c3bf1e-4875-11e3-8f56-7787f07c5a71.png)

Please review @jancborchardt @karlitschek @VicDeo or others