Added element comments to all classes of the expression parser.

Also fixed some id() implementations.

src/main/java/com/sk89q/worldedit/expression/Identifiable.java

@@ -19,6 +19,11 @@
 
 package com.sk89q.worldedit.expression;
 
+/**
+ * A common superinterface for everything passed to parser processors.
+ *
+ * @author TomyLobo
+ */
 public interface Identifiable {
     /**
      * Returns a character that helps identify the token, pseudo-token or invokable in question.