Update to Piston 0.5.2 + Doctools/Deprecation improvements (#523)

* Update to Piston 0.5.2

* [Doctools] Fix output, be verbose about deprecations

* Improve deprecation system, doctools output

worldedit-core/src/main/java/com/sk89q/worldedit/command/ToolCommands.java

@@ -88,7 +88,7 @@ public class ToolCommands {
                 ).build();
             }
             commandManager.register(CommandUtil.deprecate(
-                command, "Using global tool names is deprecated " +
+                command, "Global tool names cause conflicts " +
                 "and will be removed in WorldEdit 8", ToolCommands::asNonGlobal
             ));
         }