Names with a colon are valid (Fixes #81)

The NameManager appends a unique id for every player that has the same short name as another already existing one with a colon to the end of the clashing usernames. This is necessary so that a player can't just change their name to another user's old name and get access to all his shops.

src/main/java/com/Acrobot/ChestShop/Signs/ChestShopSign.java

@@ -25,7 +25,7 @@ public class ChestShopSign {
     public static final byte ITEM_LINE = 3;
 
     public static final Pattern[] SHOP_SIGN_PATTERN = {
-            Pattern.compile("^?[\\w -.]*$"),
+            Pattern.compile("^?[\\w -.:]*$"),
             Pattern.compile("^[1-9][0-9]*$"),
             Pattern.compile("(?i)^[\\d.bs(free) :]+$"),
             Pattern.compile("^[\\w? #:-]+$")