ENGINE-1841, fix message data transmit

Was not working when starting an event sub process because of assignement operation without target data in current process were ignored

Conflicts:
	bpm/bonita-core/bonita-process-engine/src/main/java/org/bonitasoft/engine/execution/ProcessExecutorImpl.java
fix possible npe on execute operation of start process

Conflicts:
	bpm/bonita-core/bonita-process-engine/src/main/java/org/bonitasoft/engine/execution/ProcessExecutorImpl.java
ENGINE-1770, fix intermediate event can have no incomming transitions

Conflicts:
	bpm/bonita-core/bonita-process-engine/src/main/java/org/bonitasoft/engine/execution/ProcessExecutorImpl.java