added MemberAttributeConfig serialization via XML

1. hazelcast-spring serializaion (see hazelcast-spring-3.3.xsd)
2. hazelcast serialization (see hazelcast-config-3.3.xsd)
fixing checkstyle issues
fixing checkstyle issues: tabs removed
Merge branch 'master' of https://github.com/dsukhoroslov/hazelcast.git

Conflicts:
	hazelcast/src/main/java/com/hazelcast/config/MemberAttributeConfig.java
more tabs removed
heartbeat check of clients from nodes to clear resources of unresponsive clients
checkstyle fixes
dont check timeout value of owner connection
small change
prevent data loss while promoting from second replica to owner.
check whether any registered listener exists or not before publishing event
use Clock
Merge branch 'master' of https://github.com/hazelcast/hazelcast
minor fix add not check
Merge branch 'master' of https://github.com/hazelcast/hazelcast
doc is updated with a warning about usages of null portables
Grammar revisions to Aggregators doc.
Merge branch 'master' of https://github.com/hazelcast/hazelcast
update on configuration
Merge pull request #2974 from ahmetmircik/fix/3.3/hasRegisteredListener

Fixes #2913 : Prevent extra serialization if there is no registered event listener