Authentication

GET - /keys : list possible keys
POST - /keys : create a new key for your application, parameter "url" must be supplied with the url of your project (e.g. "http://sumatra.pri.univie.ac.at/~axxxxxxx/index.php")
GET - /keys/{key} : check a key, redirect to url with token
GET - /check/{token} : check if a token is valid
GET - /user/{token} : get the username for a token