Added FutureUtil class to unify calls with multiple Future objects

Conflicts:
	hazelcast/src/main/java/com/hazelcast/util/ExceptionUtil.java
Removed some useless method overloads and lowered object allocation rate on ExceptionHandlers
Renamed test methods, fixed compile errors
Merge pull request #3107 from noctarius/github_issue_2964

Added FutureUtil class to unify calls with multiple Future objects