Synthetic operations now identifieddataserializable to reduce overhead of serialization
Fixes #419 : single partition key locality
Merge remote-tracking branch 'remotes/hazelcast/master'

Conflicts:
	stabilizer/src/main/java/com/hazelcast/stabilizer/tests/backpressure/SyntheticBackPressureTest.java
	stabilizer/src/main/java/com/hazelcast/stabilizer/tests/map/helpers/KeyUtils.java