use date picker in visualization page

pdb-ui/src/main/java/org/lucares/pdbui/domain/PlotConfig.java

@@ -4,6 +4,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import org.lucares.pdb.plot.api.Aggregate;
+import org.lucares.pdb.plot.api.DateValue;
 import org.lucares.pdb.plot.api.Limit;
 import org.lucares.pdb.plot.api.YAxisDefinition;
 
@@ -25,7 +26,7 @@ public class PlotConfig {
     private YAxisDefinition y1 = new YAxisDefinition();
     private YAxisDefinition y2 = new YAxisDefinition();
 
-    private String dateRange;
+    private DateValue dateRange;
 
     private List<Aggregate> aggregates = new ArrayList<>();
 
@@ -66,11 +67,11 @@ public class PlotConfig {
         this.limit = limit;
     }
 
-    public String getDateRange() {
+    public DateValue getDateRange() {
         return dateRange;
     }
 
-    public void setDateRange(final String dateRange) {
+    public void setDateRange(final DateValue dateRange) {
         this.dateRange = dateRange;
     }