add a datetime picker

Unfortunately the datetime picker does not support seconds. But it is
one of the few that support date and time and are flexible enough to
be used with VueJS.

pdb-plotting/src/main/java/org/lucares/pdb/plot/api/PlotSettings.java

@@ -12,7 +12,7 @@ import org.apache.commons.lang3.StringUtils;
 
 public class PlotSettings {
 
-	private static final DateTimeFormatter DATE_FORMAT = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
+	private static final DateTimeFormatter DATE_FORMAT = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
 
 	private String query;