add client class that will replace array fiddling
add ClientTest, fix a few small bugs in Client class
update Api class to use the Client class
use configuration file instead of database with applications
rename the clientsConfig.json file to clientConfig.json and update the README
remove the setConfigFile method as it is useless anyway, it will not work during callback
update README, update example registrations
update architecture picture, remove registerApplications.php script, update initDatabase