Fix writing of config values with backslashes (Fixes #444)

The VALID_PLAYERNAME_REGEXP setting needs to be changed to "^\\w+$" to work properly.

src/main/java/com/Acrobot/Breeze/Configuration/ValueParser.java

@@ -31,9 +31,9 @@ public class ValueParser {
         } else if (object instanceof String) {
             String[] lines = ((String) object).split("\\R");
             if (lines.length == 1) {
-                return '\"' + String.valueOf(object) + '\"';
+                return '\"' + String.valueOf(object).replace("\\", "\\\\") + '\"';
             } else {
-                return "|-\n" + Arrays.stream(lines).map(s -> "  " + s).collect(Collectors.joining("\n"));
+                return "|-\n" + Arrays.stream(lines).map(s -> "  " + s.replace("\\", "\\\\")).collect(Collectors.joining("\n"));
             }
         } else {
             return '\"' + String.valueOf(object) + '\"';

src/main/java/com/Acrobot/ChestShop/Configuration/Properties.java

@@ -200,7 +200,7 @@ public class Properties {
     @ConfigurationComment("This regexp validates the name of the player. If the name doesn't match, the player will neither be able to create a valid shop sign, nor buy/sell from a shop.\n" +
             "Note for Bedrock support: If you have Floodgate on your server, you should set this regexp to ^\\\\*?\\\\w+$ and ENSURE_CORRECT_PLAYERID to false\n" +
             "If your Floodgate prefix is not *, change the first * in the regexp (the one before the question mark) to whatever your prefix is.")
-    public static String VALID_PLAYERNAME_REGEXP = "^\\\\w+$";
+    public static String VALID_PLAYERNAME_REGEXP = "^\\w+$";
 
     @PrecededBySpace
     @ConfigurationComment("Should we block shops that sell things for more than they buy? (This prevents newbies from creating shops that would be exploited)")