jfg-531
check data for null values
Merge branch 'master' of github.com:griddynamics/jagger into gdmaster

Conflicts:
	webclient/src/main/java/com/griddynamics/jagger/webclient/server/WorkloadTaskDataServiceImpl.java
Merge branch 'master' of github.com:griddynamics/jagger into gdmaster
JFG-484
- new RandomLoadBalancer
- new field in schema : "randomSeed" (unsignedLong)
- parser change a little
JFG-484

+ RandomLoadBalancer
+ schema: add randomSeed field for distributors