add comment in ProjectionProfile

Author: jazzido

src/main/java/technology/tabula/ProjectionProfile.java

@@ -5,6 +5,8 @@
 import java.util.List;
 
 
+// NOTE: this class is currently not used by the extraction algorithms
+// keeping it for potential use.
 public class ProjectionProfile {
 
     public static final int DECIMAL_PLACES = 1; // fixed <-> float conversion precision