Send SMS API

 * Removes SurfnetStepupGatewayBundle and moves resources to application level
 * Creates SurfnetStepupGatewayApiBundle
There should be a way to do this more elegantly... Would've like to see the command to be composed of two other dto's: the requester (since that'll be reused for other api's as well) and the message... No need to change right now, but there is room for improvement.