Made the server tells clients what level to load...

I also added:
- A check on the client nickname encoding.
- Checks and feedback against empty or too long nicknames, empty ip, empty selection.
- The server also checks the client version now before accepting it.

Fixes #70
Removed a useless TODO and log some more.

As discussed with @hwoarangmy
Merge pull request #128 from Bertram25/development

Made the server tells clients what level to load...