Timer interval reset for states

- Add new features around Trigger to arm/disarm
  it so that state entry/exit can stop firing
  TimerTrigger. Default functionality for timer(long)
  still stays same, however timerOnce(long) will
  kick this new functionality where trigger will fire
  once after state has been entered.
- Fixes #165

spring-statemachine-samples/cdplayer/src/test/java/demo/cdplayer/CdPlayerTests.java

@@ -182,7 +182,7 @@ public class CdPlayerTests {
 		assertThat(listener.transitionCount, is(1));
 
 		listener.reset(0, 0, 0, 2);
-		assertThat(listener.transitionLatch.await(2, TimeUnit.SECONDS), is(true));
+		assertThat(listener.transitionLatch.await(2100, TimeUnit.MILLISECONDS), is(true));
 		assertThat(listener.transitionCount, is(2));
 		assertLcdStatusNotContains("00:02");
 	}