Support fork/join with regions

- Adding first changes for supporting fork and join
  concepts with regions.
- Change of some pseudostate concepts to have
  better model for this and future work.
- Fixes #39

spring-statemachine-core/src/test/resources/log4j.properties

@@ -4,5 +4,5 @@ log4j.appender.stdout=org.apache.log4j.ConsoleAppender
 log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
 log4j.appender.stdout.layout.ConversionPattern=%d{ABSOLUTE} %5p %t %c{2} [%t] - %m%n
 
-log4j.category.org.springframework.statemachine=TRACE
+log4j.category.org.springframework.statemachine=DEBUG