Remove the need to statically register service classes when using the Android Core SDK

Remove the need for static block initialisation/registration of service classes & their dependencies. i.e. this:

static {
   ServiceModuleRegistry.registerServiceModule("keycloak", KeyCloakService.class, "http");
 }

From chatting with Summers, this should be possible now that this PR is merged https://github.com/aerogear/proposals/pull/16