Separate Couchbase setup from Spring Data

This commit separates the basic setup of Couchbase from Spring Data so
that a `Bucket` and `Cluster` bucket beans are exposed even if Spring
Data is not available.

A basic setup happens if `spring.couchbase.bootstrap-hosts` is specified,
configuring the `default` bucket with no authentication unless specified
otherwise.

If Spring Data is available, those beans are re-used by default to
configure the `CouchbaseTemplate` and other repository-related beans.

Closes gh-5347

spring-boot-dependencies/pom.xml

@@ -60,6 +60,7 @@
 		<commons-digester.version>2.1</commons-digester.version>
 		<commons-pool.version>1.6</commons-pool.version>
 		<commons-pool2.version>2.4.2</commons-pool2.version>
+		<couchbase-client.version>2.2.3</couchbase-client.version>
 		<crashub.version>1.3.2</crashub.version>
 		<derby.version>10.12.1.1</derby.version>
 		<dropwizard-metrics.version>3.1.2</dropwizard-metrics.version>
@@ -133,7 +134,7 @@
 		<spring-amqp.version>1.6.0.M1</spring-amqp.version>
 		<spring-cloud-connectors.version>1.2.1.RELEASE</spring-cloud-connectors.version>
 		<spring-batch.version>3.0.6.RELEASE</spring-batch.version>
-		<spring-data-releasetrain.version>Hopper-M1</spring-data-releasetrain.version>
+		<spring-data-releasetrain.version>Hopper-BUILD-SNAPSHOT</spring-data-releasetrain.version>
 		<spring-hateoas.version>0.19.0.RELEASE</spring-hateoas.version>
 		<spring-integration.version>4.3.0.M1</spring-integration.version>
 		<spring-loaded.version>1.2.5.RELEASE</spring-loaded.version>
@@ -519,6 +520,11 @@
 				<artifactId>transactions-jta</artifactId>
 				<version>${atomikos.version}</version>
 			</dependency>
+			<dependency>
+				<groupId>com.couchbase.client</groupId>
+				<artifactId>java-client</artifactId>
+				<version>${couchbase-client.version}</version>
+			</dependency>
 			<dependency>
 				<groupId>com.datastax.cassandra</groupId>
 				<artifactId>cassandra-driver-core</artifactId>