Finally use SPI the select the service to load participants

[jesuino]

We still a manual configuration to load the current implementation, it is very ugly:

https://github.com/Jug-Vale/SorteaProjeto/blob/master/sorteia-fx/src/main/java/org/jugvale/sorteioapp/service/SorteioAppService.java#L33-L41

We need to fix it immediately