Fix concurrency issue when accessing Server's channels or queries

Fixes CLIENT-180

Change-Id: I9b0769a1001d6e0b7ae8aef96ce4d42d5d8de034
Reviewed-on: http://gerrit.dmdirc.com/1801
Automatic-Compile: DMDirc Local Commits <dmdirc@googlemail.com>
Reviewed-by: Greg Holmes <greg@dmdirc.com>

src/com/dmdirc/Server.java

 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
 import java.util.Timer;
 import java.util.TimerTask;
+import java.util.concurrent.ConcurrentSkipListMap;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
     // <editor-fold defaultstate="collapsed" desc="Instance">
 
     /** Open channels that currently exist on the server. */
-    private final Map<String, Channel> channels = new HashMap<String, Channel>();
+    private final Map<String, Channel> channels = new ConcurrentSkipListMap<String, Channel>();
 
     /** Open query windows on the server. */
-    private final Map<String, Query> queries = new HashMap<String, Query>();
+    private final Map<String, Query> queries = new ConcurrentSkipListMap<String, Query>();
 
     /** The Parser instance handling this server. */
     private Parser parser;