Polish contribution

This commit polihes the original Neo4j contribution in several areas.

Rather than providing the packages to scan, this commit rearranges the
`EntityScan` and `EntityScanRegistrar` so that the logic can be shared
for other components. If no package is provided, scanning now defaults to
the "auto-configured" package(s) and a `@NodeEntityScan` annotation
allows to override that.

The configuration has also been updated to detect the driver based on the
`uri` property. If the embedded driver is available we use that by
default. If it is not available, we're trying to connect to a Neo4j
server running on localhost. It is possible to disable the embedded mode
or set the `uri` parameter explicitly to deviate from these defaults.

The sample no longer relies on the embedded driver for licensing reason:
rather it expects an instance running on localhost (like other
data-related samples) and gracefully ignore any connection error. A
README has been added in the sample to further explain the available
options;

Closes gh-5458

spring-boot-samples/spring-boot-sample-data-neo4j/src/test/java/sample/data/neo4j/SampleNeo4jApplicationTests.java

@@ -16,35 +16,46 @@
 
 package sample.data.neo4j;
 
-import org.junit.ClassRule;
+import java.net.ConnectException;
+
+import org.junit.Rule;
 import org.junit.Test;
-import org.junit.runner.RunWith;
-import org.springframework.boot.test.IntegrationTest;
-import org.springframework.boot.test.OutputCapture;
-import org.springframework.boot.test.SpringApplicationConfiguration;
-import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import org.springframework.boot.test.rule.OutputCapture;
 
 import static org.junit.Assert.assertTrue;
 
 /**
  * Tests for {@link SampleNeo4jApplication}.
  *
- * @author Dave Syer
- * @author Andy Wilkinson
+ * @author Stephane Nicoll
  */
-@RunWith(SpringJUnit4ClassRunner.class)
-@SpringApplicationConfiguration(SampleNeo4jApplication.class)
-@IntegrationTest
 public class SampleNeo4jApplicationTests {
 
-	@ClassRule
-	public static OutputCapture outputCapture = new OutputCapture();
+	@Rule
+	public OutputCapture outputCapture = new OutputCapture();
 
 	@Test
 	public void testDefaultSettings() throws Exception {
-		String output = SampleNeo4jApplicationTests.outputCapture.toString();
+		try {
+			SampleNeo4jApplication.main(new String[0]);
+		}
+		catch (Exception ex) {
+			if (!neo4jServerRunning(ex)) {
+				return;
+			}
+		}
+		String output = this.outputCapture.toString();
 		assertTrue("Wrong output: " + output,
 				output.contains("firstName='Alice', lastName='Smith'"));
 	}
 
+	private boolean neo4jServerRunning(Throwable ex) {
+		System.out.println(ex.getMessage());
+		if (ex instanceof ConnectException) {
+			return false;
+		}
+		return (ex.getCause() == null || neo4jServerRunning(ex.getCause()));
+	}
+
 }