Trace all uri requests and sql requests + cleanup

Remember: you have to edit display.rb locally so that debug() calls output something [switch `false` to `true`] in `def debug`. Otherwise debug() calls are ignored.

Output is now readable in debug mode. Exemple (extrait):
	...
[2014-06-15 19:35:18 +0200] [debug] /js/lib/require.min.js
[2014-06-15 19:35:18 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:18 +0200] [debug] [DB] check_session
[2014-06-15 19:35:18 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:18 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:18 +0200] [debug] /favicon.ico
[2014-06-15 19:35:18 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:18 +0200] [debug] [DB] check_session
[2014-06-15 19:35:18 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:18 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:19 +0200] [debug] /css/skin/jukebox-skins.min.css
[2014-06-15 19:35:19 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:19 +0200] [debug] [DB] check_session
[2014-06-15 19:35:19 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:19 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:19 +0200] [debug] /css/jukebox.min.css
[2014-06-15 19:35:19 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:19 +0200] [debug] [DB] check_session
[2014-06-15 19:35:19 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:19 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:19 +0200] [debug] /js/lib/prototype.js
[2014-06-15 19:35:19 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:19 +0200] [debug] [DB] check_session
[2014-06-15 19:35:19 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:19 +0200] [debug] [DB] update_session_last_connexion
...
[2014-06-15 19:35:52 +0200] [debug] /api/json
[2014-06-15 19:35:52 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:52 +0200] [debug] [DB] check_session
[2014-06-15 19:35:52 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:52 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:54 +0200] [debug] /api/json
[2014-06-15 19:35:54 +0200] [debug] [DB] invalidate_sessions
[2014-06-15 19:35:54 +0200] [debug] [DB] check_session
[2014-06-15 19:35:54 +0200] [debug] [DB] update_session_last_connexion
[2014-06-15 19:35:55 +0200] [debug] [DB] update_session_last_connexion
...