Tune tests, modify web sample, add more logging

- In web sample change other event C to K which brings
  machine back from S2 to S1.
- Add more logging.
- New test sending parallel events.

spring-statemachine-samples/web/src/main/java/demo/web/StateMachineConfig.java

@@ -108,7 +108,7 @@ public class StateMachineConfig {
 					.source(States.S1).target(States.S2).event(Events.C)
 					.and()
 				.withExternal()
-					.source(States.S2).target(States.S1).event(Events.C)
+					.source(States.S2).target(States.S1).event(Events.K)
 					.and()
 				.withExternal()
 					.source(States.S1).target(States.S0).event(Events.D)
@@ -201,7 +201,7 @@ public class StateMachineConfig {
 	}
 
 	public static enum Events {
-	    A, B, C, D, E, F, G, H, I, J
+	    A, B, C, D, E, F, G, H, I, J, K
 	}
 
 	private static class FooAction implements Action<States, Events> {

spring-statemachine-samples/web/src/main/resources/static/index.html

@@ -33,6 +33,7 @@
        				<button ng-click="sendEvent('G')">event G</button>
        				<button ng-click="sendEvent('H')">event H</button>
        				<button ng-click="sendEvent('I')">event I</button>
+       				<button ng-click="sendEvent('K')">event K</button>
        			</div>
 			</div>
 			<div class="row">