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
Fixed all possible warnings (mainly by solving generics issues). Added keyword final where suitable. Added annotation @Override were suitable. Enhanced logging on problematic test by adding name of countdown latch.
Fixed ProblematicTest by using a ConcurrentHashMap instead of a HashMap.
Added support for Runnable and Callable with null as result.
Optimized support for Runnable and Callable with null as result with extended ConcurrentHashMap class.
After some discussions with Christoph we decided to use Collections.synchronizedMap() in this case, although it is not a beautiful solution.
Removed final keyword from parameter lists.
Removed final keyword from variables. Split up {} to two lines.
Fixed import wildcard.
Merge branch 'master' of https://github.com/hazelcast/hazelcast
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.
Throw serialization error when two incompatible class definitions are registered