Hopefully fixed the way the sounds are deinitialized.

It wasn't clear in the SFML doc, but the sf::Sound Object must be stopped
and deleted before the sound buffer to make sure the corresponding
OpenAL stream is detached from its sound source.

This removes a lot of random warnings on sounds when quitting OD.
Fixed dirt and Gold luminescence bug by disabling their normal appliance.

The actual fix os to apply the normal on every kind of tile and creature
but will be fixed after the entities catalog support.

Fixes #133
Merge pull request #135 from Bertram25/development

Sounds deinit + fix 133