Prevent a task from starting if an inst with the same name is running.

resolves #81

Using LockRegistryLeaderInitiator to do leadership election.

When task is started and singleInstanceEnabled isset to true then we use leader election
to determine if a task needs to be started.

Error Event Name had to be updated

spring-cloud-task-core/pom.xml

@@ -60,6 +60,16 @@
 			<groupId>org.springframework.data</groupId>
 			<artifactId>spring-data-commons</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.integration</groupId>
+			<artifactId>spring-integration-core</artifactId>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.integration</groupId>
+			<artifactId>spring-integration-jdbc</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>javax</groupId>
 			<artifactId>javaee-api</artifactId>