Cleanup invalid sessions only once in a while
1 sql request removed for each request!
Do update_session_last_connexion only once per request
1 sql request removed for each request!
Update last request datetime + login + create session only for HTML page
The idea is to avoid sql requests for .js, .css, .png ressources
Sensible gain in sql requests count
TODO: same for tokens
Remove comments
Provide an HttpSessionStateCollection mecanism to cache database sessions in RAM
Thus reduce database usage: this removes most check_session calls.
Ressources (.js, .css, .png, ...) do not create sql request anymore!
Trace all sql requests in debug mode
Show requests uri in debug mode
Comment too verbose instructions
Merge branch 'debug' into server-performance

Conflicts:
	db.rb
	http.rb
Merge pull request #34 from TiTi/server-performance

Big server performance improvement