Allow a simpler way of getting an instance of a Service class in the Android Core SDK

Allow a simpler way of getting an instance of a Service class other than below.

   keycloakService = core.getService("keycloak", KeyCloakService.class);

If there are multiple instances registered for a particular Class, it may still be necessary to use the above to get a 'named' instance (much like in dependency injection libs like spring that use annotations).
However, in most cases, the below should be possible:

keycloakService = core.getService(KeyCloakService.class);