Create UserNameConflictException Exception.

ACE-77
Define UserService interface and implement concrete MockUserService.

ACE-77
Moved UserNameConflictException to setUserName

ACE-77
Added DEFAULT_DOMAIN field which is appended to form a FQDN on login
setUserName now throws an exception if the user name is unavailable
Merge pull request #37 from ualerts-org/defineUserServiceInterface_ACE-77

Define user service interface ace 77
Merge remote-tracking branch 'origin/master' into serverBranch_ACE-76
Add domainName property and modify getName() to return full identifier

ACE-83
Modify constructor and add getFullIdentifier()

ACE-83
Refactor UserNameTest to UserIdentifierTest

Add getDomain to UserIdentifier

ACE-83
Merge remote-tracking branch
'origin/RefactorUserNameToUserIdentifier_ACE-83' into
RefactorUserNameToUserIdentifier_ACE-83

Conflicts:
	org.ualerts.chat.service/src/main/java/org/ualerts/chat/service/api/UserIdentifier.java
	org.ualerts.chat.service/src/test/java/org/ualerts/chat/service/api/concrete/UserNameTest.java