Add custom signature of batch method

[charphi]

Batch method should be customizable.

Current signature:

@ServiceDefinition ( batchType = SomeBatch.class )
interface SomeService { }

interface SomeBatch {
  Stream<SomeService > getProviders();
}

Custom signature:

@ServiceDefinition ( batchType = SomeBatch.class )
interface SomeService { }

interface SomeBatch {
  List<SomeService > getSomeServiceProviders();
}

[charphi]

Done in 8310d89