move Tags.asValueString to StringCompressor

pdb-plotting/src/main/java/org/lucares/recommind/logs/Plotter.java

@@ -208,7 +208,7 @@ public class Plotter {
     static String title(final Tags tags, final CsvSummary csvSummary) {
         // TODO title must be computed by the AggregateHandler, because it is the only
         // one knowing how many values are plotted
-        final StringBuilder result = new StringBuilder(tags.asValueString());
+        final StringBuilder result = new StringBuilder(Tags.STRING_COMPRESSOR.asValueString(tags));
 
         final int values = csvSummary.getValues();
         result.append(" (");