Refactored Conversation to account for a Participant (addParticipant,
removeParticipant, deliverMessage)
Refactored ConcreteConversationTest to consolidate adding a Participant
to a Conversation expectations
Refactored ChatClient to have a reference to a Participant. 
Added Map for Participants to Conversation. Overrode get getName method
in NullUserName to return a UUID. Refactored ConcreteConversationTest.
Created Web Controller for name check
Merge branch 'chatSessionUserName_ACE-7' of github.com:ualerts-org/ualerts-chat into chatSessionUserName_ACE-7

Conflicts:
	org.ualerts.chat.service/src/main/java/org/ualerts/chat/service/api/concrete/ConcreteParticipant.java