Removed unused PrivateConversation class.

briar-api/src/org/briarproject/api/messaging/PrivateConversation.java

-package org.briarproject.api.messaging;
-
-import org.briarproject.api.sync.Group;
-import org.briarproject.api.sync.GroupId;
-
-// TODO: Remove if no longer needed
-public class PrivateConversation {
-
-	private final Group group;
-
-	public PrivateConversation(Group group) {
-		this.group = group;
-	}
-
-	public GroupId getId() {
-		return group.getId();
-	}
-
-	public Group getGroup() {
-		return group;
-	}
-
-	@Override
-	public int hashCode() {
-		return group.hashCode();
-	}
-
-	@Override
-	public boolean equals(Object o) {
-		return o instanceof PrivateConversation
-				&& group.equals(((PrivateConversation) o).group);
-	}
-}