random source and sink
minor fix  source and sink
writer optimize
Merge remote-tracking branch 'origin/master'

Conflicts:
	org.cse.visiri.app/src/main/java/org/cse/visiri/app/sinks/EventSink.java
	org.cse.visiri.app/src/main/java/org/cse/visiri/app/sources/StockSource.java
	org.cse.visiri.communication.event-server/src/main/java/org/cse/visiri/communication/eventserver/client/EventClient.java