DATACMNS-944 - Moved to more consistent naming scheme for CrudRepository methods.

We now follow a more consistent naming scheme for the methods in repository that are driven by the following guidelines:

* Methods referring to an identifier now all end on …ById(…).
* Methods taking or returning a collection are named …All(…)

That results in the following renames:

* findOne(…) -> findById(…)
* save(Iterable) -> saveAll(Iterable)
* findAll(Iterable<ID>) -> findAllById(…)
* delete(ID) -> deleteById(ID)
* delete(Iterable<T>) -> deleteAll(Iterable<T>)
* exists() -> existsById(…)

As a side-effect of that, we can now drop the Serializable requirement for identifiers.

Updated CRUD method detection to use the new naming scheme and moved the code to Java 8 streams and Optional. Adapted RepositoryInvoker API to reflect method name changes as well.

src/main/java/org/springframework/data/domain/Auditable.java

@@ -15,7 +15,6 @@
  */
 package org.springframework.data.domain;
 
-import java.io.Serializable;
 import java.time.temporal.TemporalAccessor;
 import java.util.Optional;
 
@@ -27,7 +26,7 @@ import java.util.Optional;
  * @param <ID> the type of the audited type's identifier
  * @author Oliver Gierke
  */
-public interface Auditable<U, ID extends Serializable, T extends TemporalAccessor> extends Persistable<ID> {
+public interface Auditable<U, ID, T extends TemporalAccessor> extends Persistable<ID> {
 
 	/**
 	 * Returns the user who created this entity.

src/main/java/org/springframework/data/domain/Persistable.java

@@ -15,15 +15,13 @@
  */
 package org.springframework.data.domain;
 
-import java.io.Serializable;
-
 /**
  * Simple interface for entities.
  * 
  * @param <ID> the type of the identifier
  * @author Oliver Gierke
  */
-public interface Persistable<ID extends Serializable> extends Serializable {
+public interface Persistable<ID> {
 
 	/**
 	 * Returns the id of the entity.