Endpoint structure change poc

[Naoray]

Should be self explanatory.

• the exposed api is not changed (=devs wouldn't need to change anything).
• endpoints can be grouped in one class (called EndpointCollection -> can be changed)
• the individual requests define the resourceClass they are casted to when a response is returned.

IMO the BaseEndpointCollection is far from optimally structured, but after all it's a POC...

Atm those endpoints are implemented

$client = new MollieApiClient();
$client->setApiKey("test_xxxxxxxxxxxxxxxxxx");

$client->payments->page();
$client->payments->iterator();
$client->payments->get(..);
$client->payments->refund(..);
$client->paymentRefunds->page(..)