Add explicit declaration of batch class

[charphi]

Batch loading in @ServiceDefinition is specified by the properties batch and batchName. These properties generates a new class.
Example:

@ServiceDefinition ( batch = true, batchName = "a.b.c.SomeBatch" )
interface SomeService { }

A better approach would be to replace these properties by one that specifies the class to use.
Example:

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

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

[charphi]

Done in 6d43f0e